Hypoxia regulates CD9-mediated keratinocyte migration via the P38/MAPK pathway

A2BR facilitates the pathogenesis of H. pylori-associated GU by inducing oxidative stress through p38 MAPK phosphorylation

Gastric ulcers significantly impact the quality of life of patients, the pathogenesis of which is closely associated with Helicobacter pylori (HP) infection. Oxidative stress is involved in the pathological mechanism of gastric ulcers. Recently, adenosine A2B Receptor (A2BR) was reported to activate the p38MAPK pathway. However, the role of A2BR in gastric ulcers remains unknown. In the present study, the biological function of A2BR in HP-induced gastric ulcers was investigated to explore novel targets for gastric ulcers. GES-1 cells were infected with HP, followed by incubation with 10 μM BAY60-6583 (A2BR agonist) and 25 nM PSB1115 (A2BR antagonist). In HP-infected GES-1 cells, an increased apoptotic rate, enhanced migration ability, excessive release of reactive oxygen species (ROS), increased malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity were observed, accompanied by the activation of p38MAPK signaling, which were dramatically aggravated by BAY60-6583 and alleviated by PSB1115. In animal experiments, rats were treated with 2 mg/kg BAY60-6583 and 10 mg/kg PSB1115, followed by gastric ulcer modeling 30 min later. In HP-infected rats, increased ulcer area, elevated pepsin activity, increased hematoxylin and eosin (HE) pathological scores, increased MDA levels, and decreased SOD activity were observed, which were further aggravated by BAY60-6583 and ameliorated by PSB1115. Finally, the effects of A2BR activation on apoptosis, migration, oxidative stress, and p38MAPK signaling in HP-infected GES-1 cells were reversed by an inhibitor of the p38MAPK pathway. Collectively, A2BR facilitated the pathogenesis of HP-induced gastric ulcers by inducing oxidative stress through p38MAPK activation.

Bioelectronic microfluidic wound healing: a platform for investigating direct current stimulation of injured cell collectives

Upon cutaneous injury, the human body naturally forms an electric field (EF) that acts as a guidance cue for relevant cellular and tissue repair and reorganization. However, the direct current (DC) flow imparted by this EF can be impacted by a variety of diseases. This work delves into the impact of DC stimulation on both healthy and diabetic in vitro wound healing models of human keratinocytes, the most prevalent cell type of the skin. The culmination of non-metal electrode materials and prudent microfluidic design allowed us to create a compact bioelectronic platform to study the effects of different sustained (12 hours galvanostatic DC) EF configurations on wound closure dynamics. Specifically, we compared if electrotactically closing a wound's gap from one wound edge (i.e., uni-directional EF) is as effective as compared to alternatingly polarizing both the wound's edges (i.e., pseudo-converging EF) as both of these spatial stimulation strategies are fundamental to the eventual translational electrode design and strategy. We found that uni-directional electric guidance cues were superior in group keratinocyte healing dynamics by enhancing the wound closure rate nearly three-fold for both healthy and diabetic-like keratinocyte collectives, compared to their non-stimulated respective controls. The motility-inhibited and diabetic-like keratinocytes regained wound closure rates with uni-directional electrical stimulation (increase from 1.0 to 2.8% h^-1) comparable to their healthy non-stimulated keratinocyte counterparts (3.5% h^-1). Our results bring hope that electrical stimulation delivered in a controlled manner can be a viable pathway to accelerate wound repair, and also by providing a baseline for other researchers trying to find an optimal electrode blueprint for in vivo DC stimulation.

The Epidermal Keratinocyte as a Therapeutic Target for Management of Diabetic Wounds

Diabetes mellitus (DM) is an important cause of chronic wounds and non-traumatic amputation. The prevalence and number of cases of diabetic mellitus are increasing worldwide. Keratinocytes, the outermost layer of the epidermis, play an important role in wound healing. A high glucose environment may disrupt the physiologic functions of keratinocytes, resulting in prolonged inflammation, impaired proliferation, and the migration of keratinocytes and impaired angiogenesis. This review provides an overview of keratinocyte dysfunctions in a high glucose environment. Effective and safe therapeutic approaches for promoting diabetic wound healing can be developed if molecular mechanisms responsible for keratinocyte dysfunction in high glucose environments are elucidated.

Hypoxic preconditioning promotes galvanotaxis of human dermal microvascular endothelial cells through NF-κB pathway

Angiogenesis plays an important role in wound healing, especially in chronic wound. The directional migration of the human dermal microvascular endothelial cells (HDMECs) is the key regulation of angiogenesis. The wound healing can be regulated by numerous microenvironment factors including the electric fields, hypoxia and chemotaxis. During wound repair, the electric fields mediates the directional migration of cells and the hypoxia, which occurs immediately after injury, acts as an early stimulus to initiate the healing process. However, the mechanism of hypoxia and the endogenous electric fields coordinating to promote angiogenesis remain elusive. In this study, we observed the effect of hypoxia on the directional migration of HDMECs under electric fields. The galvanotaxis of HDMECs under the electric fields (200 mV/mm) was significantly improved, and the expression of VEGF/VEGFR2 was up-regulated after 4h of hypoxic preconditioning. In addition, the knockdown of VEGFR2 reversed the directivity of HDMECs promoted by hypoxia in the electric fields. Moreover, knockdown of VEGFR2 inhibited the migration directionality of HDMECs in the electric field after hypoxic preconditioning. Hypoxia decreased the activation of NF-κB in HDMECs. Activated NF-κB by fusicoccin decreased the expression of VEGFR2/VEGF and negatively regulated the migration direction of HDMECs in the electric fields. Enhancing the galvanotaxis response of cells might therefore be a clinically attractive approach to induce improved angiogenesis.

ADAM17 Mediates Hypoxia-Induced Keratinocyte Migration via the p38/MAPK Pathway

Although hypoxia has been shown to promote keratinocyte migration and reepithelialization, the underlying molecular mechanisms remain largely unknown. ADAM17, a member of the metalloproteinase superfamily, has been implicated in a variety of cellular behaviors such as proliferation, adhesion, and migration. ADAM17 is known to promote cancer cell migration under hypoxia, and whether or how ADAM17 plays a role in hypoxia-induced keratinocyte migration has not been identified. Here, we found that ADAM17 expression and activity were significantly promoted in keratinocytes under hypoxic condition, inhibition of ADAM17 by TAPI-2, or silencing of ADAM17 using small interfering RNA which suppressed the hypoxia-induced migration of keratinocytes significantly, indicating a pivotal role for ADAM17 in keratinocyte migration. Further, we showed that p38/MAPK was activated by hypoxia. SB203580, an inhibitor of p38/MAPK, significantly attenuated the upregulation of ADAM17 as well as the migration of keratinocytes induced by hypoxia. Activation of p38/MAPK by MKK6 (Glu) overexpression, however, had adverse effects. Taken together, our study demonstrated that hypoxia-induced keratinocyte migration requires the p38/MAPK-ADAM17 signal axis, which sheds new light on the regulatory mechanisms of keratinocyte migration. Our study might also help in developing therapeutic strategies to facilitate wound healing in vivo, where cells are migrated in a hypoxic microenvironment.

Involvement of autophagy in hypoxia-BNIP3 signaling to promote epidermal keratinocyte migration

BNIP3 is an atypical BH3-only member of the Bcl-2 family with pro-death, pro-autophagic, and cytoprotective functions, depending on the type of stress and cellular context. Recently, we demonstrated that BNIP3 stimulates the migration of epidermal keratinocytes under hypoxia. In the present study found that autophagy and BNIP3 expression were concomitantly elevated in the migrating epidermis during wound healing in a hypoxia-dependent manner. Inhibition of autophagy through lysosome-specific chemicals (CQ and BafA1) or Atg5-targeted small-interfering RNAs greatly attenuated the hypoxia-induced cell migration, and knockdown of BNIP3 in keratinocytes significantly suppressed hypoxia-induced autophagy activation and cell migration, suggesting a positive role of BNIP3-induced autophagy in keratinocyte migration. Furthermore, these results indicated that the accumulation of reactive oxygen species (ROS) by hypoxia triggered the activation of p38 and JNK mitogen-activated protein kinase (MAPK) in human immortalized keratinocyte HaCaT cells. In turn, activated p38 and JNK MAPK mediated the activation of BNIP3-induced autophagy and the enhancement of keratinocyte migration. These data revealed a previously unknown mechanism that BNIP3-induced autophagy occurs through hypoxia-induced ROS-mediated p38 and JNK MAPK activation and supports the migration of epidermal keratinocytes during wound healing.

High Glucose Suppresses Keratinocyte Migration Through the Inhibition of p38 MAPK/Autophagy Pathway

Wound healing is delayed frequently in patients with diabetes. Proper keratinocyte migration is an essential step during re-epithelialization. Impaired keratinocyte migration is a critical underlying factor responsible for the deficiency of diabetic wound healing, which is mainly attributed to the hyperglycemic state. However, the underlying mechanisms remain largely unknown. Previously, we demonstrated a marked activation of p38/mitogen-activated protein kinase (MAPK) pathway in the regenerated migrating epidermis, which in turn promoted keratinocyte migration. In the present study, we find that p38/MAPK pathway is downregulated and accompanied by inactivation of autophagy under high glucose (HG) environment. In addition, we demonstrate that inactivation of p38/MAPK and autophagy result in the inhibition of keratinocyte migration under HG environment, and the activating p38/MAPK by MKK6(Glu) overexpression rescues cell migration through an autophagy-dependent way. Moreover, diabetic wound epidermis shows a significant inhibition of p38/MAPK and autophagy. Targeting these dysfunctions may provide novel therapeutic approaches.

CD9 regulates keratinocyte migration by negatively modulating the sheddase activity of ADAM17

CD9 is a trans-membrane protein, and has recently been implicated in different physiological and cellular processes, such as cell migration and adhesion. According to previous study, down-regulation of CD9 contributes to keratinocyte migration, critical for wound re-epithelialization. Nevertheless, it is widely believed that tetraspanin CD9 does not have ligands or function as the cell surface receptor, rather it is thought to associate with other transmembrane molecules, thereby mediate keratinocyte migration. Little is known about how CD9 associates with transmembrane molecules in migratory keratinocytes. Here, using confocal microscopy, we observed that tetraspanin CD9 and ADAM17 co-localized on the surface of keratinocytes in the course of wound repair in vivo and in vitro. Co-immunoprecipitation experiments demonstrated a direct association between CD9 and ADAM17 in HaCaT cells and C57-MKs. Functional studies revealed that down-regulation or over-expression of CD9 exerted negative regulatory effects on ADAM17 sheddase activity. This activity is involved in CD9-regulated cell motility and migration. Further studies found that ADAM17 inhibitor-TAPI-2 or siADAM17 significantly abolished the enhanced effect of keratinocyte migration induced by CD9 down-regulation. Meanwhile, the sheddase activity of ADAM17 was inhibited by TAPI-2, which decreased this release of AREG and HB-EGF in CD9-silenced HaCat cells and C57-MKs. Importantly, neutralizing antibody against HB-EGF significant weakened keratinocyte migration and motility in CD9-silenced keratinocytes, and the inhibition of CD9-regulated keratinocyte migration by siADAM17 was rescued by addition of recombinant HB-EGF, activating EGFR/ERK pathway. Collectively, our results suggest that ADAM17 sheddase activity is activated by down-regulation of CD9, thereby mediating shedding of HB-EGF and activation of EGFR/ERK signaling, which crucially affects the keratinocyte migration and wound healing.

ERK activating peptide, AES16-2M promotes wound healing through accelerating migration of keratinocytes

Wound healing is an important issue that influences quality of life, and the need for products associated with wound healing is growing annually. New materials and therapies for skin wounds are being continuously researched and developed in order to increase treatment efficacy. Here, we show that the peptide AES16-2M comprised of five short amino acid sequences (REGRT) demonstrates efficacy in wound healing. AES16-2M exerted more effective healing than the control in an acute wound model, and tissue regeneration was similar to that of normal tissue in AES16-2M-treated skin. We found that the increase in re-epithelialization by AES16-2M early in wound development was due to migration of keratinocytes; a scratch assay using a human keratinocyte cell line (HaCaT) also demonstrated effective wound closure by AES16-2M. The migration of keratinocytes effected by AES16-2M was promoted through ERK phosphorylation and blocked with U0126, an ERK inhibitor. Moreover, AES16-2M treatment stimulated human dermal fibroblast (HDF) migration as well as keratinocyte. Taken together, these results suggest that AES16-2M can be an effective therapeutic agent for wound healing by promoting migration of keratinocytes and fibroblasts via ERK phosphorylation.

Notch1 Signaling Contributes to Hypoxia-induced High Expression of Integrin β1 in Keratinocyte Migration

Oxygen tension is an important micro-environmental factor that affects epidermal development and function. After injury, high oxygen consumption and vascular injury result in partial hypoxia. However, whether hypoxia benefits or hurts wound healing remains controversial. In this study, a tissue oxygen tension monitor was used to detect the spatial and temporal distribution of oxygen in burn wounds. In vitro, we demonstrate that hypoxia promoted the expression of integrin β1 and the migration of keratinocytes. Furthermore, hypoxia-induced migration was slowed by Notch1 ligands and a siRNA against ITGB1 (integrin β1). Our findings suggest that integrin β1 may be an oxygen-sensitive molecule that promotes keratinocyte migration during wound healing and that Notch1 signaling is involved in this process.

Lysozyme association with circulating RNA, extracellular vesicles, and chronic stress

BACKGROUND

Stress has demonstrated effects on inflammation though underlying cell-cell communication mechanisms remain unclear. We hypothesize that circulating RNAs and extracellular vesicles (EVs) in patients with chronic stress contain signals with functional roles in cell repair.

METHODS

Blood transcriptome from patients with Irritable Bowel Syndrome versus controls were compared to identify signaling pathways and effectors. Plasma EVs were isolated (size-exclusion chromatography) and characterized for effectors' presence (immunogold labelling-electron microscopy). Based on transcriptome pathways and EV-labelling, lysozyme's effects on cell migration were tested in human colon epithelial CRL-1790 cells and compared to the effects of CXCL12, a migration inducer (wound assay). The effect of lysozyme on immune-linked mRNA and protein levels in cells which survived following serum starvation and scratch wound were investigated (NanoString).

RESULTS

Blood transcriptomes revealed pyridoxal 5'phosphate salvage, pyrimidine ribonucleotides salvage pathways, atherosclerosis, and cell movement signaling with membrane CD9 and extracellular lysozyme as effectors. Plasma EVs showed labelling with CD9, mucins, and lysozyme. This is the first identification of lysozyme on plasma EVs. In CRL-1790 cells, lysozyme induced migration and repaired scratch wound as well as CXCL12. Immune mRNA and protein expressions were altered in cells which survived following serum starvation and scratch wound, with or without lysozyme in serum-free media post-wounding: CD9, IL8, IL6 mRNAs and CD9, NT5E, PD-L1 proteins.

CONCLUSIONS

Repair and inflammatory signals are identified in plasma EVs and circulating RNAs in chronic stress. Registered clinicaltrials.gov #NCT00824941.

GENERAL SIGNIFICANCE

This study highlights the role of circulating RNAs and EVs in stress.

Light-Emitting Diode Irradiation (640 nm) Regulates Keratinocyte Migration and Cytoskeletal Reorganization Via Hypoxia-Inducible Factor-1α

OBJECTIVE

The objective of this study was to determine the effect of light-emitting diode (LED) irradiation on the migration and proliferation of keratinocytes.

BACKGROUND DATA

Keratinocytes play a key role in re-epithelialization during wound healing; it is speculated that low-level LED therapy might improve keratinocyte migration and proliferation.

MATERIALS AND METHODS

Human keratinocyte cells (HKCs) were isolated from child or adult foreskins and irradiated with LED light with a wavelength of 640 nm and a dosage of 12 or 24 J/cm(2). Cell motility, migration, and proliferation were examined using live cell imaging, scratch assay, and a colorimetric cell counting assay, respectively. Hypoxia-inducible factor-1α (HIF-1α) protein levels were analyzed by using Western blotting. Filamentous actin (F-actin) was stained by phalloidin. YC-1 [3-(5-hydroxymethyl-2-furyl)-1-benzylindazole] was used as an HIF-1 inhibitor, and CoCl2 (cobalt chloride) and DMOG (dimethyloxaloyl glycine) are HIF-1α activators.

RESULTS

LED irradiation significantly promoted cell motility and migration, but did not significantly influence cell proliferation in HKCs. Furthermore, LED irradiation resulted in a reorganization of cellular F-actin and a dramatic upregulation of HIF-1α expression. Suppression of HIF-1α using the compound YC-1 prevented reorganization of the actin cytoskeleton following LED irradiation, suggesting that the effect of LED irradiation on the cytoskeleton is mediated through HIF-1α. Conversely, chemical activation of HIF-1α via DMOG or CoCl2 resulted in a reorganization of F-actin.

CONCLUSIONS

LED irradiation may increase keratinocyte migration via HIF-1α-dependent cytoskeletal reorganization.

The Galvanotactic Migration of Keratinocytes is Enhanced by Hypoxic Preconditioning

The endogenous electric field (EF)-directed migration of keratinocytes (galvanotaxis) into wounds is an essential step in wound re-epithelialization. Hypoxia, which occurs immediately after injury, acts as an early stimulus to initiate the healing process; however, the mechanisms for this effect, remain elusive. We show here that the galvanotactic migration of keratinocytes was enhanced by hypoxia preconditioning as a result of the increased directionality rather than the increased motility of keratinocytes. This enhancement was both oxygen tension- and preconditioning time-dependent, with the maximum effects achieved using 2% O₂ preconditioning for 6 hours. Hypoxic preconditioning (2% O₂, 6 hours) decreased the threshold voltage of galvanotaxis to < 25 mV/mm, whereas this value was between 25 and 50 mV/mm in the normal culture control. In a scratch-wound monolayer assay in which the applied EF was in the default healing direction, hypoxic preconditioning accelerated healing by 1.38-fold compared with the control conditions. Scavenging of the induced ROS by N-acetylcysteine (NAC) abolished the enhanced galvanotaxis and the accelerated healing by hypoxic preconditioning. Our data demonstrate a novel and unsuspected role of hypoxia in supporting keratinocyte galvanotaxis. Enhancing the galvanotactic response of cells might therefore be a clinically attractive approach to induce improved wound healing.