A wound-induced [Ca2+]i increase and its transcriptional activation of immediate early genes is important in the regulation of motility

Topical metformin accelerates wound healing by promoting collagen synthesis and inhibiting apoptosis in a diabetic wound model

The wound healing process, which is a pathophysiological process that includes various phases, is interrupted in diabetes due to hyperglycemia, and since deterioration occurs in these phases, a normal healing process is not observed. The aim of the current study is to investigate the proliferative and antiapoptotic effects of metformin on wound healing after topical application on diabetic and non-diabetic wounds. For this purpose, we applied metformin topically on the full-thickness excisional wound model we created in diabetic and nondiabetic groups. We investigated the effects of metformin on the apoptotic index by the Terminal deoxynucleotidyl transferase mediated dUTP Nick-End Labeling method and on collagen-I, collagen-III, p53, and c-jun expression levels by quantitative reverse transcription polymerase chain reaction technique in wound biopsy tissues. Our results showed that c-jun and p53 mRNA levels and apoptotic index increased with the effect of diabetes, while collagen synthesis was disrupted. As a result of the study, we showed that metformin increases cellular proliferation and has anti-apoptotic effects by increasing collagen-I/III expression and decreasing p53/c-jun level, especially in diabetic wounds and also in normal wounds. In conclusion, the topical effect of metformin on diabetic wounds reversed the adverse effects caused by diabetes, increasing the wound healing rate and improving the wound repair process.

p38 MAPK activation and STIM1-Orai3 association mediate TRPC6 externalization

Endothelial cell (EC) migration is critical for the repair of monolayer disruption following angioplasties, but migration is inhibited by lipid oxidation products, including lysophosphatidylcholine (lysoPC), which open canonical transient receptor potential 6 (TRPC6) channels. TRPC6 activation requires an increase in intracellular Ca2+ concentration ([Ca2+]i), the source of which is unknown. LysoPC can activate phospholipase A2 to release arachidonic acid (ArA). ArA can activate arachidonic acid-regulated calcium (ARC) channels that are formed by stromal interaction molecule 1 (STIM1) and Orai1 and Orai3 proteins. Both lysoPC and ArA can activate p38 mitogen-activated protein kinase (MAPK) that induces the phosphorylation required for STIM1-Orai3 association. This is accompanied by an increase in [Ca2+]i and TRPC6 externalization. The effect of lysoPC and ArA is not additive, suggesting activation of the same pathway. The increase in [Ca2+]i activates an Src kinase that leads to TRPC6 activation. Downregulation of Orai3 using siRNA blocks the lysoPC- or ArA-induced increase in [Ca2+]i and TRPC6 externalization and preserves EC migration. These data show that lysoPC induces activation of p38 MAPK, which leads to STIM1-Orai3 association and increased [Ca2+]i. This increase in [Ca2+]i activates an Src kinase leading to TRPC6 externalization, which initiates a cascade of events ending in cytoskeletal changes that disrupt EC migration. Blocking this pathway preserves EC migration in the presence of lipid oxidation products.NEW & NOTEWORTHY The major lysophospholipid component in oxidized LDL, lysophosphatidylcholine (lysoPC), can activate p38 MAP kinase, which in turn promotes externalization of Orai3 and STIM1-Orai3 association, suggesting involvement of arachidonic acid-regulated calcium (ARC) channels. The subsequent increase in intracellular calcium activates an Src kinase required for TRPC6 externalization. TRPC6 activation, which has been shown to inhibit endothelial cell migration, is blocked by p38 MAP kinase or Orai3 downregulation, and this partially preserves endothelial migration in lysoPC.

Activation of the cytosolic calcium-independent phospholipase A2 β isoform contributes to TRPC6 externalization via release of arachidonic acid

During vascular interventions, oxidized low-density lipoprotein and lysophosphatidylcholine (lysoPC) accumulate at the site of arterial injury, inhibiting endothelial cell (EC) migration and arterial healing. LysoPC activates canonical transient receptor potential 6 (TRPC6) channels, leading to a prolonged increase in intracellular calcium ion concentration that inhibits EC migration. However, an initial increase in intracellular calcium ion concentration is required to activate TRPC6, and this mechanism remains elusive. We hypothesized that lysoPC activates the lipid-cleaving enzyme phospholipase A₂ (PLA₂), which releases arachidonic acid (AA) from the cellular membrane to open arachidonate-regulated calcium channels, allowing calcium influx that promotes externalization and activation of TRPC6 channels. The focus of this study was to identify the roles of calcium-dependent and/or calcium-independent PLA₂ in lysoPC-induced TRPC6 externalization. We show that lysoPC induced PLA₂ enzymatic activity and caused AA release in bovine aortic ECs. To identify the specific subgroup and the isoform(s) of PLA₂ involved in lysoPC-induced TRPC6 activation, transient knockdown studies were performed in the human endothelial cell line EA.hy926 using siRNA to inhibit the expression of genes encoding cPLA₂α, cPLA₂γ, iPLA₂β, or iPLA₂γ. Downregulation of the β isoform of iPLA₂ blocked lysoPC-induced release of AA from EC membranes and TRPC6 externalization, as well as preserved EC migration in the presence of lysoPC. We propose that blocking TRPC6 activation and promoting endothelial healing could improve the outcomes for patients undergoing cardiovascular interventions.

Dominant effect of gap junction communication in wound-induced calcium-wave, NFAT activation and wound closure in keratinocytes

Wounding induces a calcium wave and disrupts the calcium gradient across the epidermis but mechanisms mediating calcium and downstream signalling, and longer-term wound healing responses are incompletely understood. As expected, live-cell confocal imaging of Fluo-4-loaded normal human keratinocytes showed an immediate increase in [Ca²⁺ ]_i at the wound edge that spread as a calcium wave (8.3 µm/s) away from the wound edge with gradually diminishing rate of rise and amplitude. The amplitude and area under the curve of [Ca²⁺ ]_i flux was increased in high (1.2 mM) [Ca²⁺ ]_o media. 18α-glycyrrhetinic acid (18αGA), a gap-junction inhibitor or hexokinase, an ATP scavenger, blocked the wound-induced calcium wave, dependent in part on [Ca²⁺ ]_o . Wounding in a high [Ca²⁺ ]_o increased nuclear factor of activated T-cells (NFAT) but not NFkB activation, assessed by dual-luciferase receptor assays compared to unwounded cells. Treatment with 18αGA or the store-operated channel blocker GSK-7975A inhibited wound-induced NFAT activation, whereas treatment with hexokinase did not. Real-time cell migration analysis, measuring wound closure rates over 24 h, revealed that 18αGA essentially blocked wound closure whereas hexokinase and GSK-7975A showed relatively minimal effects. Together these data indicate that while both gap-junction communication and ATP release from damaged cells are important in regulating the wound-induced calcium wave, long-term transcriptional and functional responses are dominantly regulated by gap-junction communication.

Signaling pathways involved in adaptive responses to cell membrane disruption

Plasma membrane disruption occurs frequently in many animal tissues. Cell membrane disruption induces not only a rapid and massive influx of Ca²⁺ into the cytosol but also an efflux or release of various signaling molecules, such as ATP, from the cytosol; in turn, these signaling molecules stimulate a variety of pathways in both wounded and non-wounded neighboring cells. These signals first trigger cell membrane repair responses in the wounded cell but then induce an adaptive response, which results in faster membrane repair in the event of future wounds in both wounded and non-wounded neighboring cells. In addition, signaling pathways stimulated by membrane disruption induce other adaptive responses, including cell survival, regeneration, migration, and proliferation. This chapter summarizes the role of intra- and intercellular signaling pathways in adaptive responses triggered by cell membrane disruption.

Review of the molecular mechanisms in wound healing: new therapeutic targets?

The restoration of the skin barrier in acute and chronic wounds is controlled by several molecular mechanisms that synergistically regulate cell kinetics, enzymatic functions, and neurovascular activation. These pathways include genetic and epigenetic activation, which modulate physiological wound healing. Our review describes the genetic background of skin repair, namely transcription-independent diffusible damage signals, individual variability, epigenetic mechanism, controlled qualitative traits, post-translational mechanisms, antioxidants, nutrients, DNA modifications, bacteria activation, mitochondrial activity, and oxidative stress. The DNA background modulating skin restoration could be used to plan new diagnostics and therapeutics.

Pathophysiological Role and Drug Modulation of Calcium Transport in Ocular Surface Cells

The ocular surface structure and extraocular accessory organs constitute the ocular surface system, which includes the cornea, conjunctiva, eyelids, lacrimal organs, and lacrimal passages. This system is composed of, and stabilized by, the corneal epithelium, conjunctival cells, conjunctival goblet cells, lacrimal acinar cells and Tenon's fibroblasts, all of which maintain the healthy eyeball surface system. Ocular surface diseases are commonly referred to corneal and conjunctival disease and external ocular disease, resulting from damage to the ocular surface structure. A growing body of evidence has indicated that abnormal activation of the KCa3.1 channel and Ca2+/ calmodulin-dependent kinase initiates ocular injury. Signaling pathways downstream of the irregular Ca2+ influx induce cell progression and migration, and impair tight junctions, epithelial transport and secretory function. In this overview, we summarize the current knowledge regarding ocular surface disease in terms of physical and pathological alteration of the ocular system. We dissect in-depth, the mechanisms underlying disease progression, and we describe the current calcium transport therapeutics and the obstacles that remain to be solved. Finally, we summarize how to integrate the research results into clinical practice in the future.

Calcium Oscillatory Behavior and Its Possible Role during Wound Healing in Bovine Corneal Endothelial Cells in Culture

In epithelial layers in culture, immediately after an injury a fast calcium wave (FCW) propagates from the wound borders toward the rest of the monolayer. We show here that similarly to other tissues, during the FCW in bovine corneal endothelial (BCE) cells in culture many cells exhibit calcium oscillations mediated by IP3 signaling. In this study we perform a detailed characterization of this oscillatory behavior and explore its possible role in the process of wound healing. In previous work we showed that, in BCE cells in culture, the healing cells undergo two stages of caspase-dependent apoptosis, at approximately two and eight hours after wounding. We determined that inhibition of the FCW greatly increases the apoptotic rate of the two stages, suggesting that the wave prevents excessive apoptosis of the healing cells. Taking this into account, we investigated the possible participation of the calcium oscillations during the FCW in apoptosis of the healing cells. For this, we employed ARL-67156 (ARL), a weak competitive inhibitor of ecto-ATPases, and the calcium chelator EGTA. We show here that, in healing BCE cells, ARL enhances cellular calcium oscillations during the FCW, while EGTA decreases oscillations. We found that ARL produces a significant decrease (to about half the control value) in the apoptotic index of the first stage of apoptosis, while EGTA increases it. Neither drug noticeably affects the second stage. We have interpreted the effect of ARL on apoptosis as due to the maintenance of moderately risen ATP levels during the FCW, which is in turn the cause for the enhancement of ATP-dependent calcium oscillations. Correspondingly, EGTA would increase the apoptotic index of the first stage by promoting a decrease in the calcium oscillatory rate. The fact that the second stage of apoptosis is not affected by the drugs suggests that the two stages are at least partially subject to different signaling pathways.

Unloading of intercellular tension induces the directional translocation of PKCα

The migration of endothelial cells (ECs) is closely associated with a Ca²⁺ -dependent protein, protein kinase Cα (PKCα). The disruption of intercellular adhesion by single-cell wounding has been shown to induce the directional translocation of PKCα. We hypothesized that this translocation of PKCα is induced by mechanical stress, such as unloading of intercellular tension, or by intercellular communication, such as gap junction-mediated and paracrine signaling. In the current study, we found that the disruption of intercellular adhesion induced the directional translocation of PKCα even when gap junction-mediated and paracrine signaling were inhibited. Conversely, it did not occur when the mechanosensitive channel was inhibited. In addition, the strain field of substrate attributable to the disruption of intercellular adhesion tended to be larger at the areas corresponding with PKCα translocation. Recently, we found that a direct mechanical stimulus induced the accumulation of PKCα at the stimulus area, involving Ca ²⁺ influx from extracellular space. These results indicated that the unloading of intercellular tension induced directional translocation of PKCα, which required Ca ²⁺ influx from extracellular space. The results of this study indicate the involvement of PKCα in the Ca ²⁺ signaling pathway in response to mechanical stress in ECs.

Wound healing of human embryonic stem cell-derived retinal pigment epithelial cells is affected by maturation stage

Background

Wound healing of retinal pigment epithelium (RPE) is a complex process that may take place in common age-related macular degeneration eye disease. The purpose of this study was to evaluate whether wounding and wound healing has an effect on Ca²⁺ dynamics in human embryonic stem cell (hESC)-RPEs cultured different periods of time.

Methods

The 9-day-cultured or 28-day-cultured hESC-RPEs from two different cell lines were wounded and the dynamics of spontaneous and mechanically induced intracellular Ca²⁺ activity was measured with live-cell Ca²⁺ imaging either immediately or 7 days after wounding. The healing time and speed were analyzed with time-lapse bright field microscopy. The Ca²⁺ activity and healing speed were analysed with image analysis. In addition the extracellular matrix deposition was assessed with confocal microscopy.

Results

The Ca²⁺ dynamics in hESC-RPE monolayers differed depending on the culture time: 9-day-cultured cells had higher number of cells with spontaneous Ca²⁺ activity close to freshly wounded edge compared to control areas, whereas in 28-day-cultured cells there was no difference in wounded and control areas. The 28-day-cultured, wounded and 7-day-healed hESC-RPEs produced wide-spreading intercellular Ca²⁺ waves upon mechanical stimulation, while in controls propagation was restricted. Most importantly, both wave spreading and spontaneous Ca²⁺ activity of cells within the healed area, as well as the cell morphology of 28-day-cultured, wounded and thereafter 7-day-healed areas resembled the 9-day-cultured hESC-RPEs.

Conclusions

This acquired knowledge about Ca²⁺ dynamics of wounded hESC-RPE monolayers is important for understanding the dynamics of RPE wound healing, and could offer a reliable functionality test for RPE cells. The data presented in here suggests that assessment of Ca²⁺ dynamics analysed with image analysis could be used as a reliable non-invasive functionality test for RPE cells.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0535-z) contains supplementary material, which is available to authorized users.

Polyamine Regulator AMD1 Promotes Cell Migration in Epidermal Wound Healing

Wound healing is a dynamic process involving gene-expression changes that drive re-epithelialization. Here, we describe an essential role for polyamine regulator AMD1 in driving cell migration at the wound edge. The polyamines, putrescine, spermidine, and spermine are small cationic molecules that play essential roles in many cellular processes. We demonstrate that AMD1 is rapidly upregulated following wounding in human skin biopsies. Knockdown of AMD1 with small hairpin RNAs causes a delay in cell migration that is rescued by the addition of spermine. We further show that spermine can promote cell migration in keratinocytes and in human ex vivo wounds, where it significantly increases epithelial tongue migration. Knockdown of AMD1 prevents the upregulation of urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor on wounding and results in a failure in actin cytoskeletal reorganization at the wound edge. We demonstrate that keratinocytes respond to wounding by modulating polyamine regulator AMD1 in order to regulate downstream gene expression and promote cell migration. This article highlights a previously unreported role for the regulation of polyamine levels and ratios in cellular behavior and fate.

New insights into the role of mitochondrial calcium homeostasis in cell migration

Mitochondria are dynamic organelles involved in numerous physiological functions. Beyond their function in ATP production, mitochondria regulate cell death, reactive oxygen species (ROS) generation, immunity and metabolism. Mitochondria also play a key role in the buffering of cytosolic calcium, and calcium transported into the matrix regulates mitochondrial metabolism. Recently, the identification of the mitochondrial calcium uniporter (MCU) and associated regulators has allowed the characterization of new physiological roles for calcium in both mitochondrial and cellular homeostasis. Indeed, recent work has highlighted the importance of mitochondrial calcium homeostasis in regulating cell migration. Cell migration is a property common to all metazoans and is critical to embryogenesis, cancer progression, wound-healing and immune surveillance. Previous work has established that cytoplasmic calcium is a key regulator of cell migration, as oscillations in cytosolic calcium activate cytoskeletal remodelling, actin contraction and focal adhesion (FA) turnover necessary for cell movement. Recent work using animal models and in cellulo experiments to genetically modulate MCU and partners have shed new light on the role of mitochondrial calcium dynamics in cytoskeletal remodelling through the modulation of ATP and ROS production, as well as intracellular calcium signalling. This review focuses on MCU and its regulators in cell migration during physiological and pathophysiological processes including development and cancer. We also present hypotheses to explain the molecular mechanisms by which MCU may regulate mitochondrial dynamics and motility to drive cell migration.

Single-Cell Defects Cause a Long-Range Mechanical Response in a Confluent Epithelial Cell Layer

Epithelial cells are responsible for tissue homeostasis and form a barrier to maintain chemical gradients and mechanical integrity. Therefore, rapid wound closure is crucial for proper tissue function and restoring homeostasis. In this study, the mechanical properties of cells surrounding a single-cell wound are investigated during closure of the defect. The single-cell wound is induced in an intact layer using micropipette action and responses in neighboring cells are monitored with atomic force microscopy. Direct neighbors reveal a rise in the apparent pretension, which is dominated by cortical tension. The same effect was observed for a single-cell wound induced by laser ablation and during closure of a not fully confluent layer. Moreover, changes in the apparent pretension are far reaching and persist even in cells separated by three cell widths from the defect. This shows that epithelial cells respond to minimal wounds in a collective fashion by increased contractility with substantial reach.

Biphasic and directed translocation of protein kinase Cα inside cultured endothelial cells before migration

Mechanical wounding of an endothelial monolayer induces an immediate Ca²⁺ wave. Several hours later, the denuded area is covered by endothelial cells (ECs) that migrate to the wound. This migration process is closely related to protein kinase Cα (PKCα), a Ca²⁺-dependent protein that translocates from the cytosol to the cell membrane. Because the cells adjacent to the wounded area are the first to migrate into the wound, we investigated whether a mechanical wound immediately induces PKCα translocation in adjacent cells. We monitored Ca²⁺ dynamics and PKCα translocation simultaneously using fluorescent microscopy. For this simultaneous observation, we used Fura-2–acetoxymethyl ester to visualize Ca²⁺ and constructed a green fluorescent protein-tagged fusion protein to visualize PKCα. Mechanical wounding of the endothelial monolayer induced an immediate Ca²⁺ wave in cells adjacent to the wounded cells before their migration. Almost concurrently, PKCα in the neighboring cells translocated to the cell membrane, then accumulated at the periphery near the wounded cell. This report is the first description of this biphasic and directed translocation of PKCα in cells before cell migration. Our results may provide new insights into the directed migration of ECs.

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We wounded a single endothelial cell (EC) and investigated the distribution of protein kinase Cα (PKCα) in adjacent ECs.

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Initially, PKCα translocates to the cell membrane.

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Thereafter, PKCα accumulates at the cell periphery adjacent to the wounded cell.

Integration of TRPC6 and NADPH oxidase activation in lysophosphatidylcholine-induced TRPC5 externalization

Lipid oxidation products, including lysophosphatidylcholine (lysoPC), activate canonical transient receptor potential 6 (TRPC6) channels, and the subsequent increase in intracellular Ca²⁺ leads to TRPC5 activation. The goal of this study is to elucidate the steps in the pathway between TRPC6 activation and TRPC5 externalization. Following TRPC6 activation by lysoPC, extracellular regulated kinase (ERK) is phosphorylated. This leads to phosphorylation of p47^phox and subsequent NADPH oxidase activation with increased production of reactive oxygen species. ERK activation requires TRPC6 opening and influx of Ca²⁺ as evidenced by the failure of lysoPC to induce ERK phosphorylation in TRPC6^-/- endothelial cells. ERK siRNA blocks the lysoPC-induced activation of NADPH oxidase, demonstrating that ERK activation is upstream of NADPH oxidase. The reactive oxygen species produced by NADPH oxidase promote myosin light chain kinase (MLCK) activation with phosphorylation of MLC and TRPC5 externalization. Downregulation of ERK, NADPH oxidase, or MLCK with the relevant siRNA prevents TRPC5 externalization. Blocking MLCK activation prevents the prolonged rise in intracellular calcium levels and preserves endothelial migration in the presence of lysoPC.

Collective cell migration has distinct directionality and speed dynamics

When a constraint is removed, confluent cells migrate directionally into the available space. How the migration directionality and speed increase are initiated at the leading edge and propagate into neighboring cells are not well understood. Using a quantitative visualization technique-Particle Image Velocimetry (PIV)-we revealed that migration directionality and speed had strikingly different dynamics. Migration directionality increases as a wave propagating from the leading edge into the cell sheet, while the increase in cell migration speed is maintained only at the leading edge. The overall directionality steadily increases with time as cells migrate into the cell-free space, but migration speed remains largely the same. A particle-based compass (PBC) model suggests cellular interplay (which depends on cell-cell distance) and migration speed are sufficient to capture the dynamics of migration directionality revealed experimentally. Extracellular Ca²⁺ regulated both migration speed and directionality, but in a significantly different way, suggested by the correlation between directionality and speed only in some dynamic ranges. Our experimental and modeling results reveal distinct directionality and speed dynamics in collective migration, and these factors can be regulated by extracellular Ca²⁺ through cellular interplay. Quantitative visualization using PIV and our PBC model thus provide a powerful approach to dissect the mechanisms of collective cell migration.

The Epithelial Sodium Channel and the Processes of Wound Healing

The epithelial sodium channel (ENaC) mediates passive sodium transport across the apical membranes of sodium absorbing epithelia, like the distal nephron, the intestine, and the lung airways. Additionally, the channel has been involved in the transduction of mechanical stimuli, such as hydrostatic pressure, membrane stretch, and shear stress from fluid flow. Thus, in vascular endothelium, it participates in the control of the vascular tone via its activity both as a sodium channel and as a shear stress transducer. Rather recently, ENaC has been shown to participate in the processes of wound healing, a role that may also involve its activities as sodium transporter and as mechanotransducer. Its presence as the sole channel mediating sodium transport in many tissues and the diversity of its functions probably underlie the complexity of its regulation. This brief review describes some aspects of ENaC regulation, comments on evidence about ENaC participation in wound healing, and suggests possible regulatory mechanisms involved in this participation.

Suppression of transient receptor potential melastatin 4 expression promotes conversion of endothelial cells into fibroblasts via transforming growth factor/activin receptor-like kinase 5 pathway

OBJECTIVE

To study whether transient receptor potential melastatin 4 (TRPM4) participates in endothelial fibrosis and to investigate the underlying mechanism.

METHODS

Primary human endothelial cells were used and pharmacological and short interfering RNA-based approaches were used to test the transforming growth factor beta (TGF-β)/activin receptor-like kinase 5 (ALK5) pathway participation and contribution of TRPM7 ion channel.

RESULTS

Suppression of TRPM4 expression leads to decreased endothelial protein expression and increased expression of fibrotic and extracellular matrix markers. Furthermore, TRPM4 downregulation increases intracellular Ca levels as a potential condition for fibrosis. The underlying mechanism of endothelial fibrosis shows that inhibition of TRPM4 expression induces TGF-β1 and TGF-β2 expression, which act through their receptor, ALK5, and the nuclear translocation of the profibrotic transcription factor smad4.

CONCLUSION

TRPM4 acts to maintain endothelial features and its loss promotes fibrotic conversion via TGF-β production. The regulation of TRPM4 levels could be a target for preserving endothelial function during inflammatory diseases.

Fast calcium wave inhibits excessive apoptosis during epithelial wound healing

Successful wound closure is mainly the result of two cellular processes: migration and proliferation. Apoptosis has also been suggested to play a role in the mechanisms of wound healing. The fast calcium wave (FCW), triggered immediately after a wound is produced, has been proposed to be involved in determining healing responses in epithelia. We have explored the effects of the reversible inhibition of FCW on the apoptotic and proliferative responses of healing bovine corneal endothelial (BCE) cells in culture. The most important findings of this study are that caspase-dependent apoptosis occurs during the healing process, that the amount of apoptosis has a linear dependence on the migrated distance, and that FCW inhibition greatly increases the apoptotic index. We have further been able to establish that FCW plays a role in the control of cell proliferation during BCE wound healing. These results indicate that one of the main roles of the wave is to inhibit an excessive apoptotic response of the healing migrating cells. This property might represent a basic mechanism to allow sufficient migration and proliferation of the healing cells to assure proper restitution of the injured tissue.

Membrane translocation of TRPC6 channels and endothelial migration are regulated by calmodulin and PI3 kinase activation

Lipid oxidation products, including lysophosphatidylcholine (lysoPC), activate canonical transient receptor potential 6 (TRPC6) channels leading to inhibition of endothelial cell (EC) migration in vitro and delayed EC healing of arterial injuries in vivo. The precise mechanism through which lysoPC activates TRPC6 channels is not known, but calmodulin (CaM) contributes to the regulation of TRPC channels. Using site-directed mutagenesis, cDNAs were generated in which Tyr(99) or Tyr(138) of CaM was replaced with Phe, generating mutant CaM, Phe(99)-CaM, or Phe(138)-CaM, respectively. In ECs transiently transfected with pcDNA3.1-myc-His-Phe(99)-CaM, but not in ECs transfected with pcDNA3.1-myc-His-Phe(138)-CaM, the lysoPC-induced TRPC6-CaM dissociation and TRPC6 externalization was disrupted. Also, the lysoPC-induced increase in intracellular calcium concentration was inhibited in ECs transiently transfected with pcDNA3.1-myc-His-Phe(99)-CaM. Blocking phosphorylation of CaM at Tyr(99) also reduced CaM association with the p85 subunit and subsequent activation of phosphatidylinositol 3-kinase (PI3K). This prevented the increase in phosphatidylinositol (3,4,5)-trisphosphate (PIP3) and the translocation of TRPC6 to the cell membrane and reduced the inhibition of EC migration by lysoPC. These findings suggest that lysoPC induces CaM phosphorylation at Tyr(99) by a Src family kinase and that phosphorylated CaM activates PI3K to produce PIP3, which promotes TRPC6 translocation to the cell membrane.

C. elegans epidermal wounding induces a mitochondrial ROS burst that promotes wound repair

Reactive oxygen species (ROS) such as hydrogen peroxide are generated at wound sites and act as long-range signals in wound healing. The roles of other ROS in wound repair are little explored. Here, we reveal a cytoprotective role for mitochondrial ROS (mtROS) in Caenorhabditis elegans skin wound healing. We show that skin wounding causes local production of mtROS superoxide at the wound site. Inhibition of mtROS levels by mitochondrial superoxide-specific antioxidants blocks actin-based wound closure, whereas elevation of mtROS promotes wound closure and enhances survival of mutant animals defective in wound healing. mtROS act downstream of wound-triggered Ca(2+) influx. We find that the mitochondrial calcium uniporter MCU-1 is essential for rapid mitochondrial Ca(2+) uptake and mtROS production after wounding. mtROS can promote wound closure by local inhibition of Rho GTPase activity via a redox-sensitive motif. These findings delineate a pathway acting via mtROS that promotes cytoskeletal responses in wound healing.

Endotoxin-induced vascular endothelial cell migration is dependent on TLR4/NF-κB pathway, NAD(P)H oxidase activation, and transient receptor potential melastatin 7 calcium channel activity

Endothelial dysfunction is decisive and leads to the development of several inflammatory diseases. Endotoxemia-derived sepsis syndrome exhibits a broad inflammation-induced endothelial dysfunction. We reported previously that the endotoxin, lipopolysaccharide (LPS), induces the conversion of endothelial cells (ECs) into activated fibroblasts, showing a myofibroblast-like protein expression profile. Enhanced migration is a hallmark of myofibroblast function. However, the mechanism involved in LPS-induced EC migration is no totally understood. Some studies have shown that the transient receptor potential melastatin 7 (TRPM7) ion channel is involved in fibroblast and tumor cell migration through the regulation of calcium influx. Furthermore, LPS modulates TRPM7 expression. However, whether TRPM7 is involved in LPS-induced EC migration remains unknown. Here, we study the participation of LPS as an inducer of EC migration and study the mechanism underlying evaluating the participation of the TRPM7 ion channel. Our results demonstrate that LPS induced EC migration in a dose-dependent manner. Furthermore, this migratory process was mediated by the TLR-4/NF-κB pathway and the generation of ROS through the PKC-activated NAD(P)H oxidase. In addition, LPS increased the intracellular calcium level and the number of focal adhesion kinase (FAK)-positive focal adhesions in EC. Finally, we demonstrate that using TRPM7 blockers or suppressing TRPM7 expression through siRNA successfully inhibits the calcium influx and the LPS-induced EC migration. These results point out TRPM7 as a new target in the drug design for several inflammatory diseases that impair vascular endothelium function.

Low-frequency pulsed electromagnetic fields significantly improve time of closure and proliferation of human tendon fibroblasts

Background

The promotion of the healing process following musculoskeletal injuries comprises growth factor signalling, migration, proliferation and apoptosis of cells. If these processes could be modulated, the healing of tendon tissue may be markedly enhanced. Here, we report the use of the Somagen™ device, which is certified for medical use according to European laws. It generates low-frequency pulsed electromagnetic fields that trigger effects of a nature that are yet to be determined.

Methods

A 1.5-cm wide, linear scrape was introduced into patellar tendon fibroblast cultures (N = 5 donors). Treatment was carried out every second day. The regimen was applied three times in total with 30 minutes comprising pulsed electromagnetic field packages with two fundamental frequencies (10 minutes of 33 Hz, 20 minutes of 7.8 Hz). Control cells remained untreated. All samples were analyzed for gap closure time, proliferation and apoptosis one week after induction of the scrape wound.

Results

The mean time for bridging the gap in the nontreated cells was 5.05 ± 0.33 days, and in treated cells, it took 3.35 ± 0.38 days (P <0.001). For cell cultures with scrape wounds, a mean value for BrdU incorporation of OD = 0.70 ± 0.16 was found. Whereas low-frequency pulsed electromagnetic fields treated samples showed OD = 1.58 ± 0.24 (P <0.001). However, the percentage of apoptotic cells did not differ between the two groups.

Conclusions

Our data demonstrate that low-frequency pulsed electromagnetic fields emitted by the Somagen™ device influences the in vitro wound healing of patellar tendon fibroblasts and, therefore, possibly increases wound healing potential.

Hypercholesterolemia inhibits re-endothelialization of arterial injuries by TRPC channel activation

OBJECTIVE

After arterial injury, endothelial cell (EC) migration is essential for healing, but lipid oxidation products activate TRPC6 and TRPC5 ion channels, leading to increased intracellular calcium and inhibition of EC migration in vitro. The objective of this study was to further evaluate the role of TRPC channels in EC migration in vitro and to validate in vitro findings in an in vivo model.

METHODS

Mouse aortic ECs were cultured, and the effect of lysophosphatidylcholine, the major lysophospholipid in oxidized low-density lipoprotein, on migration was assessed in a razor-scrape assay. EC healing after a carotid injury with electrocautery was evaluated in wild-type (WT), TRPC6(-/-), and TRPC5(-/-) mice receiving either a chow or high-cholesterol (HC) diet.

RESULTS

Lysophosphatidylcholine inhibited EC migration of WT ECs to 22% of baseline and of TRPC5(-/-) ECs to 53% of baseline but had minimal effect on TRPC6(-/-) EC migration. Hypercholesterolemia severely impaired EC healing in vivo, with 51.4% ± 1.8% and 24.9% ± 2.0% of the injury resurfaced with ECs at 5 days in chow-fed and HC-fed WT mice, respectively (P < .001). Hypercholesterolemia did not impair healing in TRPC6(-/-) mice, with coverage of 48.4% ± 3.4% and 46.8% ± 1.6% in chow-fed and HC-fed TRPC6(-/-) mice, respectively. Hypercholesterolemia had a reduced inhibitory effect in TRPC5(-/-) mice, with EC coverage of 51.7% ± 3.0% and 37.% ± 1.4% in chow-fed and HC-fed TRPC5(-/-) mice, respectively.

CONCLUSIONS

Results suggest that activation of TRPC6 and TRPC5 channels is the key contributor to impaired endothelial healing of arterial injuries in hypercholesterolemic mice.

Voltage-gated sodium channel Nav 1.5 contributes to astrogliosis in an in vitro model of glial injury via reverse Na+ /Ca2+ exchange

Astrogliosis is a prominent feature of many, if not all, pathologies of the brain and spinal cord, yet a detailed understanding of the underlying molecular pathways involved in the transformation from quiescent to reactive astrocyte remains elusive. We investigated the contribution of voltage-gated sodium channels to astrogliosis in an in vitro model of mechanical injury to astrocytes. Previous studies have shown that a scratch injury to astrocytes invokes dual mechanisms of migration and proliferation in these cells. Our results demonstrate that wound closure after mechanical injury, involving both migration and proliferation, is attenuated by pharmacological treatment with tetrodotoxin (TTX) and KB-R7943, at a dose that blocks reverse mode of the Na(+) /Ca(2+) exchanger (NCX), and by knockdown of Nav 1.5 mRNA. We also show that astrocytes display a robust [Ca(2+) ]i transient after mechanical injury and demonstrate that this [Ca(2+) ]i response is also attenuated by TTX, KB-R7943, and Nav 1.5 mRNA knockdown. Our results suggest that Nav 1.5 and NCX are potential targets for modulation of astrogliosis after injury via their effect on [Ca(2+) ]i .

Endotoxin induces fibrosis in vascular endothelial cells through a mechanism dependent on transient receptor protein melastatin 7 activity

The pathogenesis of systemic inflammatory diseases, including endotoxemia-derived sepsis syndrome, is characterized by endothelial dysfunction. It has been demonstrated that the endotoxin lipopolysaccharide (LPS) induces the conversion of endothelial cells (ECs) into activated fibroblasts through endothelial-to-mesenchymal transition mechanism. Fibrogenesis is highly dependent on intracellular Ca2+ concentration increases through the participation of calcium channels. However, the specific molecular identity of the calcium channel that mediates the Ca2+ influx during endotoxin-induced endothelial fibrosis is still unknown. Transient receptor potential melastatin 7 (TRPM7) is a calcium channel that is expressed in many cell types, including ECs. TRPM7 is involved in a number of crucial processes such as the conversion of fibroblasts into activated fibroblasts, or myofibroblasts, being responsible for the development of several characteristics of them. However, the role of the TRPM7 ion channel in endotoxin-induced endothelial fibrosis is unknown. Thus, our aim was to study whether the TRPM7 calcium channel participates in endotoxin-induced endothelial fibrosis. Using primary cultures of ECs, we demonstrated that TRPM7 is a crucial protein involved in endotoxin-induced endothelial fibrosis. Suppression of TRPM7 expression protected ECs from the fibrogenic process stimulated by endotoxin. Downregulation of TRPM7 prevented the endotoxin-induced endothelial markers decrease and fibrotic genes increase in ECs. In addition, TRPM7 downregulation abolished the endotoxin-induced increase in ECM proteins in ECs. Furthermore, we showed that intracellular Ca2+ levels were greatly increased upon LPS challenge in a mechanism dependent on TRPM7 expression. These results demonstrate that TRPM7 is a key protein involved in the mechanism underlying endotoxin-induced endothelial fibrosis.

Increases in reactive oxygen species enhance vascular endothelial cell migration through a mechanism dependent on the transient receptor potential melastatin 4 ion channel

A hallmark of severe inflammation is reactive oxygen species (ROS) overproduction induced by increased inflammatory mediators secretion. During systemic inflammation, inflammation mediators circulating in the bloodstream interact with endothelial cells (ECs) raising intracellular oxidative stress at the endothelial monolayer. Oxidative stress mediates several pathological functions, including an exacerbated EC migration. Because cell migration critically depends on calcium channel-mediated Ca(2+) influx, the molecular identification of the calcium channel involved in oxidative stress-modulated EC migration has been the subject of intense investigation. The transient receptor potential melastatin 4 (TRPM4) protein is a ROS-modulated non-selective cationic channel that performs several cell functions, including regulating intracellular Ca(2+) overload and Ca(2+) oscillation. This channel is expressed in multiple tissues, including ECs, and contributes to the migration of certain immune cells. However, whether the TRPM4 ion channel participates in oxidative stress-mediated EC migration is not known. Herein, we investigate whether oxidative stress initiates or enhances EC migration and study the role played by the ROS-modulated TRPM4 ion channel in oxidative stress-mediated EC migration. We demonstrate that oxidative stress enhances, but does not initiate, EC migration in a dose-dependent manner. Notably, we demonstrate that the TRPM4 ion channel is critical in promoting H2O2-enhanced EC migration. These results show that TRPM4 is a novel pharmacological target for the possible treatment of severe inflammation and other oxidative stress-mediated inflammatory diseases.

The role of transcription-independent damage signals in the initiation of epithelial wound healing

Wound healing is an essential biological process that comprises sequential steps aimed at restoring the architecture and function of damaged cells and tissues. This process begins with conserved damage signals, such as Ca(2+), hydrogen peroxide (H2O2) and ATP, that diffuse through epithelial tissues and initiate immediate gene transcription-independent cellular effects, including cell shape changes, the formation of functional actomyosin structures and the recruitment of immune cells. These events integrate the ensuing transcription of specific wound response genes that further advance the wound healing response. The immediate importance of transcription-independent damage signals illustrates that healing a wound begins as soon as damage occurs.

Role of ion channels and transporters in cell migration

Cell motility is central to tissue homeostasis in health and disease, and there is hardly any cell in the body that is not motile at a given point in its life cycle. Important physiological processes intimately related to the ability of the respective cells to migrate include embryogenesis, immune defense, angiogenesis, and wound healing. On the other side, migration is associated with life-threatening pathologies such as tumor metastases and atherosclerosis. Research from the last ≈ 15 years revealed that ion channels and transporters are indispensable components of the cellular migration apparatus. After presenting general principles by which transport proteins affect cell migration, we will discuss systematically the role of channels and transporters involved in cell migration.

Thymosin β4 is rapidly internalized by cells and does not induce intracellular Ca2+ elevation

Thymosin β4 (Tβ4) is a multifunctional protein that has pleiotropic activities both intracellularly and extracellularly. The mechanisms by which it influences cellular processes such as adhesion, migration, differentiation, or apoptosis are not yet understood. Calcium is a ubiquitous signal molecule that is involved in the regulation of almost all cellular functions. Our data indicate that the release of Ca(2+) from intracellular stores following stimulation of cells with Tβ4 does not occur. Interestingly, Tβ4 becomes rapidly internalized, supporting the concept that it may express its activities via intracellular receptors.

Interactions between the amnioserosa and the epidermis revealed by the function of the u-shaped gene

Dorsal closure (DC) is an essential step during Drosophila development whereby a hole is sealed in the dorsal epidermis and serves as a model for cell sheet morphogenesis and wound healing. It involves the orchestrated interplay of transcriptional networks and dynamic regulation of cell machinery to bring about shape changes, mechanical forces, and emergent properties. Here we provide insight into the regulation of dorsal closure by describing novel autonomous and non-autonomous roles for U-shaped (Ush) in the amnioserosa, the epidermis, and in mediation of communication between the tissues. We identified Ush by gene expression microarray analysis of Dpp signaling targets and show that Ush mediates some DC functions of Dpp. By selectively restoring Ush function in either the AS or the epidermis in ush mutants, we show that the AS makes a greater (Ush-dependent) contribution to closure than the epidermis. A signal from the AS induces epidermal cell elongation and JNK activation in the DME, while cable formation requires Ush on both sides of the leading edge, i.e. in both the AS and epidermis. Our study demonstrates that the amnioserosa and epidermis communicate at several steps during the process: sometimes the epidermis instructs the amnioserosa, other times the AS instructs the epidermis, and still other times they appear to collaborate.

The mechanism of injury-induced intracellular calcium concentration oscillations in the endothelium of excised rat aorta

Endothelial injury is the primary event that leads to a variety of severe vascular disorders. Mechanical injury elicits a Ca(2+) response in the endothelium of excised rat aorta, which comprises an initial Ca(2+) release from inositol-1,4,5-trisphosphate (InsP(3))-sensitive stores followed by a long-lasting decay phase due to Ca(2+) entry through uncoupled connexons. The Ca(2+) signal may also adopt an oscillatory pattern, the molecular underpinnings of which are unclear. In the light of the role played by Ca(2+) spiking in tissue regeneration, this study aimed to unveil the mechanisms underlying injury-induced Ca(2+) oscillations. The latter reversibly ceased upon removal of extracellular Ca(2+) or addition of the gap junction blockers heptanol, 18 α,β-glycyrrhetinic acid, La(3+) and Ni(2+), but were insensitive to BTP-2 and SKF 96365. The spiking response was abolished by inhibiting the Ca(2+) entry mode of the Na(+)/Ca(2+) exchanger (NCX). The InsP(3)-producing agonist ATP resumed Ca(2+) oscillations in silent cells, while the phospholipase C inhibitor U73122 suppressed them. Injury-induced Ca(2+) transients were prevented by the sarcoplasmic-endoplasmic reticulum calcium ATPase (SERCA) blockers thapsigargin and cyclopiazonic acid, while they were unaffected by suramin and genistein. These data show for the first time that the coordinated interplay between NCX-mediated Ca(2+) entry and InsP(3)-dependent Ca(2+) release contributes to injury-induced intracellular Ca(2+) concentration oscillations.

CaMK-II promotes focal adhesion turnover and cell motility by inducing tyrosine dephosphorylation of FAK and paxillin

Transient elevations in Ca2+ have previously been shown to promote focal adhesion disassembly and cell motility through an unknown mechanism. In this study, evidence is provided to show that CaMK-II, a Ca2+/calmodulin dependent protein kinase, influences fibroblast adhesion and motility. TIRF microscopy reveals a dynamic population of CaMK-II at the cell surface in migrating cells. Inhibition of CaMK-II with two mechanistically distinct, membrane permeant inhibitors (KN-93 and myr-AIP) freezes lamellipodial dynamics, accelerates spreading on fibronectin, enlarges paxillin-containing focal adhesions and blocks cell motility. In contrast, constitutively active CaMK-II is not found at the cell surface, reduces cell attachment, eliminates paxillin from focal adhesions and decreases the phospho-tyrosine levels of both FAK and paxillin; all of these events can be reversed with myr-AIP. Thus, both CaMK-II inhibition and constitutive activation block cell motility through over-stabilization or destabilization of focal adhesions, respectively. Coupled with the existence of transient Ca2+ elevations and a dynamic CaMK-II population, these findings provide the first direct evidence that CaMK-II enables cell motility by transiently and locally stimulating tyrosine dephosphorylation of focal adhesion proteins to promote focal adhesion turnover.

Glycogen synthase kinase 3beta regulation of nuclear factor of activated T-cells isoform c1 in the vascular smooth muscle cell response to injury

The migration and proliferation of vascular smooth muscle cells (vSMCs) are critical events in neointima formation during atherosclerosis and restenosis. The transcription factor nuclear factor of activated T-cells-isoform c1 (NFATc1) is regulated by atherogenic cytokines, and has been implicated in the migratory and proliferative responses of vSMCs through the regulation of gene expression. In T-cells, calcineurin de-phosphorylates NFATc1, leading to its nuclear import, while glycogen synthase kinase 3 beta (GSK3beta) phosphorylates NFATc1 and promotes its nuclear export. However, the relationship between NFATc1 and GSK3beta has not been studied during SMC migration and proliferation. We investigated this by scrape wounding vSMCs in vitro, and studying wound repair. NFATc1 protein was transiently increased, reaching a peak at 8 h after wounding. Cell fractionation and immunocytochemistry revealed that NFATc1 accumulation in the nucleus was maximal at 4 h after injury, and this was coincident with a significant 9 fold increase in transcriptional activity. Silencing NFATc1 expression with siRNA or inhibition of NFAT with cyclosporin A (CsA) attenuated wound closure by vSMCs. Phospho-GSK3beta (inactive) increased to a peak at 30 min after injury, preceding the nuclear accumulation of NFATc1. Overexpression of a constitutively active mutant of GSK3beta delayed the nuclear accumulation of NFATc1, caused a 50% decrease in NFAT transcriptional activity, and attenuated vSMC wound repair. We conclude that NFATc1 promotes the vSMC response to injury, and that inhibition of GSK3beta is required for the activation of NFAT during wound repair.

Phospholipase C-delta extends intercellular signalling range and responses to injury-released growth factors in non-excitable cells

OBJECTIVES

Intercellular communication in non-excitable cells is restricted to a limited range close to the signal source. Here, we have examined whether modification of the intracellular microenvironment could prolong the spatial proposition of signal generation and could increase cell proliferation.

MATERIAL AND METHODS

Mathematical models and experimental studies of endothelial repair after controlled mechanical injury were used. The models predict the diffusion range of injury-released growth factors and identify important parameters involved in a signalling regenerative mode. Transfected human umbilical vein endothelial cells (HUVECs) were used to validate model results, by examining intercellular calcium signalling range, cell proliferation and wound healing rate.

RESULTS

The models predict that growth factors have a limited capacity of extracellular diffusion and that intercellular signals are specially sensitive to cell phospholipase C-delta (PLCdelta) levels. As basal PLCdelta levels are increased by transfection, a significantly increased intercellular calcium range, enhanced cell proliferation, and faster wound healing rate were observed.

CONCLUSION

Our in silico and in vitro studies demonstrated that non-excitable endothelial cells respond to stimuli in a complex manner, in which intercellular communication is controlled by physicochemical properties of the stimulus and by the cell microenvironment. Such findings may have profound implications for our understanding of the tight nature of autocrine cell growth control, compensation to stress states and response to altered microenvironment, under pathological conditions.

Elucidation of a TRPC6-TRPC5 channel cascade that restricts endothelial cell movement

Canonical transient receptor potential (TRPC) channels are opened by classical signal transduction events initiated by receptor activation or depletion of intracellular calcium stores. Here, we report a novel mechanism for opening TRPC channels in which TRPC6 activation initiates a cascade resulting in TRPC5 translocation. When endothelial cells (ECs) are incubated in lysophosphatidylcholine (lysoPC), rapid translocation of TRPC6 initiates calcium influx that results in externalization of TRPC5. Activation of this TRPC6-5 cascade causes a prolonged increase in intracellular calcium concentration ([Ca(2+)](i)) that inhibits EC movement. When TRPC5 is down-regulated with siRNA, the lysoPC-induced rise in [Ca(2+)](i) is shortened and the inhibition of EC migration is lessened. When TRPC6 is down-regulated or EC from TRPC6(-/-) mice are studied, lysoPC has minimal effect on [Ca(2+)](i) and EC migration. In addition, TRPC5 is not externalized in response to lysoPC, supporting the dependence of TRPC5 translocation on the opening of TRPC6 channels. Activation of this novel TRPC channel cascade by lysoPC, resulting in the inhibition of EC migration, could adversely impact on EC healing in atherosclerotic arteries where lysoPC is abundant.

Ca2+ signaling in injured in situ endothelium of rat aorta

The inner wall of excised rat aorta was scraped by a microelectrode and Ca2+ signals were investigated by fluorescence microscopy in endothelial cells (ECs) directly coupled with injured cells. The injury caused an immediate increase in the intracellular Ca2+ concentration ([Ca2+]i), followed by a long-lasting decay phase due to Ca2+ influx from extracellular space. The immediate response was mainly due to activation of purinergic receptors, as shown by the effect of P2X and P2Y receptors agonists and antagonists, such as suramin, alpha,beta-MeATP, MRS-2179 and 2-MeSAMP. Inhibition of store-operated Ca2+ influx did not affect either the peak response or the decay phase. Furthermore, the latter was: (i) insensitive to phospholipase C inhibition, (ii) sensitive to the gap junction blockers, palmitoleic acid, heptanol, octanol and oleamide, and (iii) sensitive to La3+ and Ni2+, but not to Gd3+. Finally, ethidium bromide or Lucifer Yellow did not enter ECs facing the scraped area. These results suggest that endothelium scraping: (i) causes a short-lasting stimulation of healthy ECs by extracellular nucleotides released from damaged cells and (ii) uncouples the hemichannels of the ECs facing the injury site; these hemichannels do not fully close and allow a long-lasting Ca2+ entry.

Characterization of stress-responsive CIPK genes in rice for stress tolerance improvement

Plants respond to adverse environments by initiating a series of signaling processes that often involves diverse protein kinases, including calcineurin B-like protein-interacting protein kinases (CIPKs). In this study, putative CIPK genes (OsCIPK01-OsCIPK30) in the rice (Oryza sativa) genome were surveyed for their transcriptional responses to various abiotic stresses. The results showed that 20 OsCIPK genes were differentially induced by at least one of the stresses, including drought, salinity, cold, polyethylene glycol, and abscisic acid treatment. Most of the genes induced by drought or salt stress were also induced by abscisic acid treatment but not by cold. A few CIPK genes containing none of the reported stress-responsive cis-elements in their promoter regions were also induced by multiple stresses. To prove that some of these stress-responsive OsCIPK genes are potentially useful for stress-tolerance improvement, three CIPK genes (OsCIPK03, OsCIPK12, and OsCIPK15) were overexpressed in japonica rice 'Zhonghua 11'. Transgenic plants overexpressing the transgenes OsCIPK03, OsCIPK12, and OsCIPK15 showed significantly improved tolerance to cold, drought, and salt stress, respectively. Under cold and drought stresses, OsCIPK03- and OsCIPK12-overexpressing transgenic plants accumulated significantly higher contents of proline and soluble sugars than the wild type. Putative proline synthetase and transporter genes had significantly higher expression level in the transgenic plants than in the wild type. The differentially induced expression of OsCIPK genes by different stresses and the examples of improved stress tolerance of the OsCIPK transgenic rice suggest that rice CIPK genes have diverse roles in different stress responses and some of them may possess potential usefulness in stress-tolerance improvement of rice.

A novel function of capsaicin-sensitive TRPV1 channels: Involvement in cell migration

Cell migration relies on a tight temporal and spatial regulation of the intracellular Ca2+ concentration ([Ca2+]i). [Ca2+]i in turn depends on Ca2+ influx via channels in the plasma membrane whose molecular nature is still largely unknown for migrating cells. A mechanosensitive component of the Ca2+ influx pathway was suggested. We show here that the capsaicin-sensitive transient receptor potential channel TRPV1, that plays an important role in pain transduction, is one of the Ca2+ influx channels involved in cell migration. Activating TRPV1 channels with capsaicin leads to an acceleration of human hepatoblastoma (HepG2) cells pretreated with hepatocyte growth factor (HGF). The speed rises by up to 50% and the displacement is doubled. Patch clamp experiments revealed the presence of capsaicin and resiniferatoxin (RTX)-sensitive currents. In contrast, HepG2 cells kept in the absence of HGF are not accelerated by capsaicin and express no capsaicin- or RTX-sensitive current. The TRPV1 antagonist capsazepine prevents the stimulation of migration and inhibits capsaicin-sensitive currents. Finally, we compared the contribution of capsaicin-sensitive TRPV1 channels to cell migration with that of mechanosensitive TRPV4 channels that are also expressed in HepG2 cells. A specific TRPV4 agonist, 4alpha-phorbol 12,13-didecanoate, does not increase the displacement. In summary, we assigned a novel role to capsaicin-sensitive TRPV1 channels. They are important Ca2+ influx channels required for cell migration.

An automatic procedure for evaluation of single cell motility

BACKGROUND

Cell motility is vital in many physiological and pathological processes, such as embryogenesis, inflammation, wound healing, and metastasis. However, the time-consuming step in the evaluation of individual cell motility is the analysis of hundreds of recorded images of cell cultures in general consisting of retrieving images, one at a time, and marking the positions of individual cells by a computer mouse. Therefore, the aim of the present study was to develop a novel automatic procedure for the evaluation of cell motility.

MATERIALS AND METHODS

The procedure was tested on fibroblasts and glioma and adenocarcinoma cells engineered to express the green fluorescent protein by either transient transfection or adenovirus transduction, allowing automatic recognition of cell coordinates on retrieved images.

RESULTS

The effects of serum growth factors, teratogenic compounds, and overexpression of transcription factors on the motile behavior of cultured cells were determined. Cell motility was estimated by both manual and automatic marking of cell position and subsequently motility parameters were computed. The results obtained by the two procedures were found to correlate significantly.

CONCLUSIONS

We developed a procedure allowing automatic video recording of sparsely seeded cells transfected with a plasmid or tranduced with a recombinant virus expressing the enhanced green fluorescent protein (EGFP).

Citrate enhances in vitro metastatic behaviours of PC-3M human prostate cancer cells: Status of endogenous citrate and dependence on aconitase and fatty acid synthase

Prostate is a unique organ that produces and releases large amounts of citrate. This is reduced significantly in cancer and it is possible that citrate is (re)taken up and used as a metabolite to enhance cellular activity. The main purpose of this study was to determine how cytosolic citrate might affect in vitro metastatic cell behaviours (lateral motility, endocytosis and adhesion). Normal (PNT2-C2) and metastatic (PC-3M) human prostate cancer cells were used in a comparative approach. As regards intermediary metabolic enzymes, aconitase and fatty acid synthase, already implicated in prostate cancer, were evaluated. The level of intracellular citrate was significantly higher in PNT2-C2 cells under both control conditions and following preincubation in extracellular citrate. Supply of exogenous citrate enhanced endocytosis, lateral motility, decreased cell adhesion of PC-3M cells but failed to produce any effect on normal cells. Real-time PCR measurements showed that the mRNA levels of mitochondrial and cytosolic aconitases and fatty acid synthase were significantly higher in PC-3M cells. Correspondingly, aconitase activity was also higher in PC-3M cells. Using cerulenin (an inhibitor of fatty acid synthase), oxalomalate and fluorocitrate (inhibiting aconitases), we investigated the dependence of citrate-induced down-regulation of cellular adhesion on aconitase and fatty acid synthase activities. It was concluded: (1) that strongly metastatic PC-3M cells stored less/utilised more cytosolic citrate than the normal PNT2-C2 cells and (2) that cancer cells could metabolise cytoplasmic citrate via aconitase and fatty acid synthase to enhance their metastatic behaviour.

ADAM10 mediates E-cadherin shedding and regulates epithelial cell-cell adhesion, migration, and beta-catenin translocation

E-cadherin controls a wide array of cellular behaviors, including cell-cell adhesion, differentiation, and tissue development. We show here that E-cadherin is cleaved specifically by ADAM (a disintegrin and metalloprotease) 10 in its ectodomain. Analysis of ADAM10-deficient fibroblasts, inhibitor studies, and RNA interference-mediated down-regulation of ADAM10 demonstrated that ADAM10 is responsible not only for the constitutive shedding but also for the regulated shedding of this adhesion molecule in fibroblasts and keratinocytes. ADAM10-mediated E-cadherin shedding affects epithelial cell-cell adhesion as well as cell migration. Furthermore, the shedding of E-cadherin by ADAM10 modulates the beta-catenin subcellular localization and downstream signaling. ADAM10 overexpression in epithelial cells increased the expression of the beta-catenin downstream gene cyclin D1 dose-dependently and enhanced cell proliferation. In ADAM10-deficient mouse embryos, the C-terminal E-cadherin fragment is not generated, and the full-length protein accumulates, highlighting the in vivo relevance for ADAM10 in E-cadherin shedding. Our data strongly suggest that this protease constitutes a major regulatory element for the multiple functions of E-cadherin under physiological as well as pathological conditions.

Adhesion-dependent activation of CaMKII and regulation of ERK activation in vascular smooth muscle

Cell adhesion-dependent activation of ERK1/2 has been linked functionally to focal adhesion dynamics. We previously reported that in adherent vascular smooth muscle (VSM) cells, CaMKII mediates ERK1/2 activation in response to Ca(2+)-mobilizing stimuli. In the present study, we tested whether CaMKII regulates ERK1/2 signaling in response to VSM cell adhesion. Using an antibody that specifically recognizes CaMKII autophosphorylated on Thr(287), we determined that CaMKII is rapidly activated (within 1 min) after the adherence of cells on multiple ECM substrates. Activation of CaMKII on fibronectin was unaffected in cells overexpressing focal adhesion kinase (FAK)-related nonkinase (FRNK), an endogenous inhibitor of FAK. Furthermore, CaMKII was rapidly and robustly activated in VSM cells plated on poly-l-lysine. These results suggest that adhesion-dependent CaMKII activation is integrin independent. Adhesion-dependent FAK activation on fibronectin was not affected in cells treated with the selective CaMKII inhibitor KN-93 (30 muM) or in cells in which the expression of CaMKII with small interfering RNA (siRNA) was suppressed, although tyrosine phosphorylation of paxillin was inhibited in CaMKII-delta(2)-suppressed cells. Sustained ERK1/2 activation that was dependent on FAK activation (inhibited by FRNK) was also attenuated by CaMKII inhibition or siRNA-mediated gene silencing. Rapid ERK1/2 activation that preceded FAK and paxillin activation was detected upon VSM cell adhesion to poly-l-lysine, and this response was inhibited by CaMKII gene silencing. These results indicate that integrin-independent CaMKII activation is an early signal during VSM cell adhesion that positively modulates ERK1/2 signaling through FAK-dependent and FAK-independent mechanisms.