Hypoxia induces epidermal keratinocyte matrix metalloproteinase-9 secretion via the protein kinase C pathway

Enhancing pressure ulcer healing and tissue regeneration by using N-acetyl-cysteine loaded carboxymethyl cellulose/gelatin/sodium alginate hydrogel

Prolonged pressure on the skin can result in pressure ulcers, which may lead to serious complications, such as infection and tissue damage. In this study, we evaluated the effect of a carboxymethyl cellulose/gelatin/sodium alginate (CMC/Gel/Alg) hydrogel containing N-acetyl-cysteine (NAC) on the healing of pressure ulcers. Pressure ulcers were induced by applying a magnet to the dorsum of rat skin. The wounds were then treated with sterile gauze, ChitoHeal Gel®, and CMC/Gel/Alg hydrogel dressings with or without NAC for the other groups. We evaluated the morphology, weight loss, swelling, rheology, blood compatibility, cytocompatibility, antioxidant capacity, and wound scratch of the prepared hydrogel. MTT assay revealed that the optimum concentration of NAC was 5 mg/ml, which induced higher cell proliferation and viability. Results of the histopathological evaluation showed increased wound closure, and complete re-epithelialization in the hydrogel-containing NAC group compared to the other groups. The CMC/Gel/Alg/5 mg/ml NAC hydrogel dressing showed 84% wound closure at 14 days after treatment. Immunohistochemical results showed a decrease in the level of TNF-α on day 14 compared day 7. Results of the qPCR assay revealed that NAC hydrogel increased the expression of Collagen type I and TGF-β1 and decreased MMP2 and MMP9 mRNA on the 14th day. The results suggest that the CMC/Gel/Alg/5 mg/ml NAC hydrogel with antioxidant properties is an appropriate dressing for wound healing.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

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.

HIF-1α Metabolic Pathways in Human Cancer

Oxygen is directly involved in many key pathophysiological processes. Oxygen deficiency, also known as hypoxia, could have adverse effects on mammalian cells, with ischemia in vital tissues being the most significant (Michiels C. Physiological and pathological responses to hypoxia. Am J Pathol 164(6): 1875-1882, 2004); therefore, timely adaptive responses to variations in oxygen availability are essential for cellular homeostasis and survival. The most critical molecular event in hypoxic response is the activation and stabilization of a transcriptional factor termed hypoxia-induced factor-1 (HIF-1) that is responsible for the upregulation of many downstream effector genes, collectively known as hypoxia-responsive genes. Multiple key biological pathways such as proliferation, energy metabolism, invasion, and metastasis are governed by these genes; thus, HIF-1-mediated pathways are equally pivotal in both physiology and pathology.As we gain knowledge on the molecular mechanisms underlying the regulation of HIF-1, a great focus has been placed on elucidating the cellular function of HIF-1, particularly the role of HIF-1 in cancer pathogenesis pathways such as proliferation, invasion, angiogenesis, and metastasis. In cancer, HIF-1 is directly involved in the shift of cancer tissues from oxidative phosphorylation to aerobic glycolysis, a phenomenon known as the Warburg effect. Although targeting HIF-1 as a cancer therapy seems like an extremely rational approach, owing to the complex network of its downstream effector genes, the development of specific HIF-1 inhibitors with fewer side effects and more specificity has not been achieved. Therefore, in this review, we provide a brief background about the function of HIF proteins in hypoxia response with a special emphasis on the unique role played by HIF-1α in cancer growth and invasiveness, in the hypoxia response context.

Matrix metalloproteinase 9 induces keratinocyte apoptosis through FasL/Fas pathway in diabetic wound

Apoptosis is a mechanism to remove unwanted cells in the tissue. In diabetic wound, which is characterized by delayed healing process, excessive apoptosis is documented and plays a crucial role. Matrix metalloproteinase 9 (MMP9), which is elevated in non-healed diabetic wound, is necessary for healing process but its abnormality resulted in a delayed healing. The classical function of MMP9 is the degradation of extracellular matrix (ECM). However, there is some literature evidence that MMP9 triggers cell apoptosis. Whether the excessive MMP9 contributes to epidermis cell apoptosis in delayed healing diabetic wound and the underlying mechanisms is not clear. In this study, we aimed to explore whether MMP9 induced keratinocyte apoptosis and investigate the plausible mechanisms. Our in vitro study showed that advanced glycation end products (AGEs) induced keratinocyte apoptosis and enhanced MMP9 level. Besides, MMP9, both intra-cellular expressions and extra-cellular supplement, promoted cell apoptosis. Further, MMP9 resulted in an increased expression of FasL, other than Fas and p53. These findings identified a novel effect that MMP9 exerted in delayed diabetic wound healing, owing to a pro-apoptotic effect on keratinocyte, which was mediated by an increase of FasL expression. This study increases understanding of elevated MMP9 which is involved in diabetic wound repair and offers some insights into novel future therapies.

Reperfusion Microvascular Ischemia After Prolonged Coronary Occlusion: Implications And Treatment With Local Supersaturated Oxygen Delivery

Following a prolonged coronary arterial occlusion, heterogeneously scattered, focal regions of low erythrocyte flow are commonly found throughout the reperfused myocardium. Experimental studies have also demonstrated the presence of widespread, focally patchy regions of microvascular ischemia during reperfusion (RMI). However, the potential contribution of RMI to tissue viability and function has received little attention in the absence of practical clinical methods for its detection. In this review, the anatomic/functional basis of RMI is summarized, along with the evidence for its presence in reperfused myocardium. Advances in microcirculation research related to obstructive responses of vascular endothelial cells and blood elements to the effects of hypoxia and low shear stress are discussed, and a potential cycle of intensification of RMI from such responses and progressive loss of functional capillary density is presented. In capillaries with impaired erythrocyte flow, compensatory increases in the delivery of oxygen, because of its low solubility in plasma, are effective only at high partial pressures. As discussed herein, attenuation of the cycle with oxygen at hyperbaric levels in plasma is, very likely, responsible for improved tissue level perfusion noted experimentally. Observed clinical benefits from intracoronary SuperSaturated oxygen (SSO₂) delivery, including infarct size reduction, can be attributed to attenuation of RMI with improvement in microvascular blood flow.

Effect of Hypoxia on Gene Expression in Cell Populations Involved in Wound Healing

Wound healing is a complex process regulated by multiple signals and consisting of several phases known as haemostasis, inflammation, proliferation, and remodelling. Keratinocytes, endothelial cells, macrophages, and fibroblasts are the major cell populations involved in wound healing process. Hypoxia plays a critical role in this process since cells sense and respond to hypoxic conditions by changing gene expression. This study assessed the in vitro expression of 77 genes involved in angiogenesis, metabolism, cell growth, proliferation and apoptosis in human keratinocytes (HaCaT), microvascular endothelial cells (HMEC-1), differentiated macrophages (THP-1), and dermal fibroblasts (HDF). Results indicated that the gene expression profiles induced by hypoxia were cell-type specific. In HMEC-1 and differentiated THP-1, most of the genes modulated by hypoxia encode proteins involved in angiogenesis or belonging to cytokines and growth factors. In HaCaT and HDF, hypoxia mainly affected the expression of genes encoding proteins involved in cell metabolism. This work can help to enlarge the current knowledge about the mechanisms through which a hypoxic environment influences wound healing processes at the molecular level.

TIMP-1-Mediated Chemoresistance via Induction of IL-6 in NSCLC

Elevated tissue inhibitor of metalloproteinase-1 (TIMP-1) is a negative prognosticator in non-small cell lung carcinoma NSCLC patients. This study sought to identify mechanisms whereby TIMP-1 impacts anticancer therapy. Using NSCLC cells and their TIMP-1 knockdown clones, we examined the chemoresistance against two chemotherapeutic agents, Gemcitabine and Cisplatin, as identified by increased apoptosis in the knockdown clones. A bead-based cytokine screening assay identified interleukin-6 (IL-6) as a key factor in chemoresistance. Exogenous human recombinant rhTIMP-1 or rhIL-6 resulted in reduced apoptosis. IL-6 expression was closely correlated with TIMP-1 kinetics and was upregulated by the addition of exogenous TIMP-1 while TIMP-1 neutralizing antibodies delayed IL-6 elevation. IL-6 production was regulated by TIMP-1, exerting its effect via activation of downstream signal transducer and activator of transcription 3 (STAT3) signaling. Both molecules and their documented transcription factors were upregulated and activated in chemoresistant NSCLC cells, confirming the roles of TIMP-1 and IL-6 in chemoresistance. To examine the role of these genes in patients, survival data from lung adenocarcinoma (LUAD) patients was curated from the cancer genome atlas (TCGA) database. Kaplan-Meier analysis found that individuals expressing low TIMP-1 and IL-6 have a higher survival rate and that the two-gene signature was more significant than the single-gene status. We define for the first time, a regulatory relationship between TIMP-1 and IL-6 in NSCLCs, suggesting that the TIMP-1/IL6 axis may be a valuable prognostic biomarker. Therapeutic interventions directed at this dual target may improve overall prognosis while negatively affecting the development of chemoresistance in NSCLC.

Hypoxia-Induced Epithelial-To-Mesenchymal Transition Mediates Fibroblast Abnormalities via ERK Activation in Cutaneous Wound Healing

Previous studies described the involvement of extracellular signal-related kinase (ERK) in systemic fibrotic diseases, but the role of ERK in cutaneous scarring is unknown. Although hypoxia drives tissue fibrosis by activating hypoxia-inducible factor-1α (HIF-1α), the specific roles of hypoxia and associated ERK phosphorylation in abnormal fibroblast activity during cutaneous scarring are unclear. Here, we investigated whether pathologic myofibroblast-like keloid fibroblast activity is promoted by hypoxia-induced epithelial-mesenchymal transition mediated by ERK activation. ERK phosphorylation was significantly increased in keloid tissue and fibroblasts. Human dermal fibroblasts cultured under hypoxia (1% O₂) expressed phosphorylated ERK and exhibited activation of p38 mitogen-activated protein kinase signaling. Hypoxic human dermal fibroblasts showed increased protein and mRNA levels of epithelial-mesenchymal transition markers. Furthermore, administration of an ERK inhibitor (SCH772984) reduced the hypoxia-induced elevation of collagen type I levels in human dermal fibroblasts. Therefore, ERK may be a promising therapeutic target in profibrogenic diseases.

Intermittent hypoxia induces beneficial cardiovascular remodeling in left ventricular function of type 1 diabetic rat

OBJECTIVE

Depressed mechanical activity is a marked complication in diabetics. Hypoxia has properties for novel diagnostic and therapeutic strategies, while intermittent hypoxia (IH) provides early functional and histologic remodeling, including some cardio benefits in early hemodynamic alterations with histologic remodeling and delayed changes in peripheral vasoreactivity. Therefore, we aimed to examine whether IH application presents a cardioprotective effect, via stabilization of hypoxia-inducible factor (HIF) in streptozotocin (STZ)-induced diabetic rat heart.

METHODS

Male 10-week-old Wistar rats were randomly assigned as control group (C), IH group, (STZ)-induced diabetic group (DM) and IH applied DM group (DM+IH). Diabetes duration was kept 6 weeks and IH groups were exposed to hypobaric hypoxia at about 70 kPa (including ~14% PO2; 6 h/day for 6-weeks).

RESULTS

Depressed left ventricular developed pressure (LVDP) and prolonged contraction and relaxation of Langendorff-perfused hearts, as well as increased total oxidative status from streptozotocin (STZ)-induced diabetic rats were markedly prevented with IH application. IH application induced significant increase in protein expression levels of both HIF-1α and vascular endothelial growth factor (VEGF), in both control and diabetic rat hearts, whereas there were significant decreases in the protein levels of prolyl-4 hydroxylase domain enzymes, PHD2, and PHD3 in diabetic hearts. Furthermore, IH application induced marked increases in protein levels of matrix metalloproteinases, MMP-2 and MMP-9 and capillary density in left ventricle of diabetic rats.

CONCLUSION

Overall, we presented how IH application has a beneficial cardiovascular remodeling effect in left ventricular function of diabetic rats, at most, via affecting increased oxidative stress and HIF-VEGF related angiogenesis, providing information on hyperglycemia associated new targets and therapeutic strategies.

Expression of tissue inhibitor of metalloproteinases and matrix metalloproteinases in the ischemic brain of photothrombosis model mice

Middle cerebral artery occlusion (MCAO) is the most widely used animal model of ischemic stroke. This model well recapitulates the pathological features of most human cases; however, MCAO is technically difficult to achieve in mice and has some disadvantages for investigating the molecular mechanisms of pathological progression in stroke. The recently developed photothrombosis model may be more suitable for research on the molecular mechanisms of ischemic stroke in mice. Yet, similarities and differences between the photothrombosis and MCAO models are not well characterized. In the present study, we examined the expression of tissue inhibitor of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs) in the brains of photothrombosis model mice. Our results indicated that the gene expression of TIMP-1 was upregulated in endothelial cells in the pathological area surrounding the infarction, similar to the MCAO model. Yet, pathologically induced changes in TIMP-1 were not affected by treatment with aspirin or etodolac. Whereas MMP-2 and MMP-8 mRNA were upregulated after infarction in both models, MMP-9 expression, which is induced in the infarct area in the MCAO model, was unchanged in the photothrombosis model. These findings suggest that the expression patterns of TIMP-1 and MMP-9 are regulated independently in photothrombosis model mice.

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.

Effects of curcumin on hypoxia-inducible factor as a new therapeutic target

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that consists of two subunits, the HIF-1α and HIF-1β (ARNT). Under hypoxic conditions, HIF-1 is an adaptive system that regulates the transcription of multiple genes associated with growth, angiogenesis, proliferation, glucose transport, metabolism, pH regulation and cell death. However, aberrant HIF-1 activation contributes to the pathophysiology of several human diseases such as cancer, ischemic cardiovascular disorders, and pulmonary and kidney diseases. A growing body of evidence indicates that curcumin, a natural bioactive compound of turmeric root, significantly targets both HIF-1 subunits, but is more potent against HIF-1α. In this review, we have summarized the knowledge about the pharmacological effects of curcumin on HIF-1 and the related molecular mechanisms that may be effective candidates for the development of multi-targeted therapy for several human diseases.

Foxn1 expression in keratinocytes is stimulated by hypoxia: further evidence of its role in skin wound healing

Recent studies have shown that the transcription factor Foxn1, which is expressed in keratinocytes, is involved in the skin wound healing process, yet how Foxn1 functions remains largely unknown. Our latest data indicate that Foxn1 drives skin healing via engagement in re-epithelization and the epithelial-mesenchymal transition (EMT) process. In the present study, 2D-DIGE proteomic profiling analysis of in vitro cultured keratinocytes transfected with adenoviral vector carrying Foxn1-GFP or GFP alone (control) revealed forty proteins with differential abundance between the compared groups. Among the proteins with Foxn1-dependent expression, several enable adaptation to hypoxia. Subsequent experiments revealed that hypoxic conditions (1% O₂) stimulate endogenous and exogenous (transfected Ad-Foxn1) Foxn1 expression in cultured keratinocytes. A proteomics analysis also identified proteins that can act as a factors controlling the balance between cell proliferation, differentiation and apoptosis in response to Foxn1. We also showed that in C57BL/6 keratinocytes, the stimulation of Foxn1 by hypoxia is accompanied by increases in Mmp-9 expression. These data corroborate the detected co-localization of Foxn1 and Mmp-9 expression in vivo in post-wounding skin samples of Foxn1::Egfp transgenic mice. Together, our data indicate that Foxn1 orchestrates cellular changes in keratinocytes in both physiological (self-renewal) and pathological (skin wound healing) contexts.

An update on anticancer drug development and delivery targeting carbonic anhydrase IX

The expression of carbonic anhydrase (CA) IX is up-regulated in many types of solid tumors in humans under hypoxic and acidic microenvironment. Inhibition of CA IX enzymatic activity with selective inhibitors, antibodies or labeled probes has been shown to reverse the acidic environment of solid tumors and reduce the tumor growth establishing the significant role of CA IX in tumorigenesis. Thus, the development of potent antitumor drugs targeting CA IX with minimal toxic effects is important for the target-specific tumor therapy. Recently, several promising antitumor agents against CA IX have been developed to treat certain types of cancers in combination with radiation and chemotherapy. Here we review the inhibition of CA IX by small molecule compounds and monoclonal antibodies. The methods of enzymatic assays, biophysical methods, animal models including zebrafish and Xenopus oocytes, and techniques of diagnostic imaging to detect hypoxic tumors using CA IX-targeted conjugates are discussed with the aim to overview the recent progress related to novel therapeutic agents that target CA IX in hypoxic tumors.

Mold Alkaloid Cytochalasin D Modifies the Morphology and Secretion of fMLP-, LPS-, or PMA-Stimulated Neutrophils upon Adhesion to Fibronectin

Neutrophils play an essential role in innate immunity due to their ability to migrate into infected tissues and kill microbes with bactericides located in their secretory granules. Neutrophil transmigration and degranulation are tightly regulated by actin cytoskeleton. Invading pathogens produce alkaloids that cause the depolymerization of actin, such as the mold alkaloid cytochalasin D. We studied the effect of cytochalasin D on the morphology and secretion of fMLP-, LPS-, or PMA-stimulated human neutrophils upon adhesion to fibronectin. Electron microscopy showed that the morphology of the neutrophils adherent to fibronectin in the presence of various stimuli differed. But in the presence of cytochalasin D, all stimulated neutrophils exhibited a uniform nonspread shape and developed thread-like membrane tubulovesicular extensions (cytonemes) measuring 200 nm in diameter. Simultaneous detection of neutrophil secretory products by mass spectrometry showed that all tested stimuli caused the secretion of MMP-9, a key enzyme in the neutrophil migration. Cytochalasin D impaired the MMP-9 secretion but initiated the release of cathepsin G and other granular bactericides, proinflammatory agents. The release of bactericides apparently occurs through the formation, shedding, and lysis of cytonemes. The production of alkaloids which modify neutrophil responses to stimulation via actin depolymerization may be part of the strategy of pathogen invasion.

Extracellular matrix remodeling in equine sarcoid: an immunohistochemical and molecular study

BACKGROUND

Equine sarcoids are locally invasive, fibroblastic benign skin tumors. Bovine papillomavirus type-1 (BPV-1) and/or Bovine papillomavirus type-2 (BPV-2) are believed to be the causative agent of sarcoids, although the mechanisms by which the virus induce the tumor are still poorly understood. We hypothesized that in genetically predisposed equines latent BPV infection may be reactivated by immunosoppression and/or mechanical injury leading to a form of pathologic wound which may transform into a sarcoid. In this study, we investigated in 25 equine sarcoids and in five normal skin samples the histological features and evaluated the immunohistochemical and molecular expression of type I and type III Collagen, vimentin (VIM), alfa Smooth Muscle Actin (α-SMA), Matrix Metalloproteinase (MMPs) -2, 9, 14 and tissue inhibitor of metalloproteinase 2 (TIMP-2).

RESULTS

In 64% of investigated sarcoids, type I collagen staining was stronger than that of type III collagen. In 80% of sarcoids, SFs were strongly positive for vimentin and negative for α-SMA; the remaining sarcoid samples (20%) showed 70-80% of SFs labeled for vim and approximately 20-30% labeled for α-SMA. Moreover, all sarcoid specimen showed a variable staining pattern (weak to moderate) for MMP-9 and MMP-14, and a moderate to strong staining for MMP-2 and TIMP-2. Biochemical analysis confirmed immunohistochemical results and showed in sarcoids, for the first time, the cleaved form of MMP9, the 35 KDa active species for MMP-9.

CONCLUSIONS

This study revealed that in equine sarcoids exhibit an altered turnover of the Extracellular Matrix (ECM) deposition and degradation, as result of an altered expression of MMPs and TIMPs. Therefore, these observations seem to confirm that the basic mechanism for growth of equine sarcoids could be a neoplastic transformation during wound healing.

Cross Talk between Proliferative, Angiogenic, and Cellular Mechanisms Orchestred by HIF-1α in Psoriasis

Psoriasis is a chronic inflammatory skin disease where the altered regulation in angiogenesis, inflammation, and proliferation of keratinocytes are the possible causes of the disease, and the transcription factor “hypoxia-inducible factor 1-alpha” (HIF-1α) is involved in the homeostasis of these three biological phenomena. In this review, the role of HIF-1α in the cross talk between the cytokines and cells of the immunological system involved in the pathogenesis of psoriasis is discussed.

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

Keratinocyte migration is an early event in the wound healing process. Although we previously found that CD9 downregulation is required for the keratinocyte migration during wound repair, the mechanism of how CD9 expression is regulated remains unclear. Here, we observed the effect of hypoxia (2% O2) on CD9 expression and keratinocyte migration. CD9 expression was downregulated and keratinocyte migration was increased under hypoxic conditions. In addition, CD9 overexpression reversed hypoxia-induced cell migration. We also found that hypoxia activated the p38/MAPK pathway. SB203580, a p38/MAPK inhibitor, increased CD9 expression and inhibited keratinocyte migration under hypoxia, while MKK6 (Glu) overexpression decreased CD9 expression and promoted hypoxic keratinocyte migration. Our results demonstrate that hypoxia regulates CD9 expression and CD9-mediated keratinocyte migration via the p38/MAPK pathway.

The role of Hypoxia-inducible factor-1 α , glucose transporter-1, (GLUT-1) and carbon anhydrase IX in endometrial cancer patients

Hypoxia-inducible factor-1α (HIF-1α), glucose transporter-1 (GLUT-1), and carbon anhydrase IX (CAIX) are important molecules that allow adaptation to hypoxic environments. The aim of our study was to investigate the correlation between HIF-1α, GLUT-1, and CAIX protein level with the clinicopathological features of endometrial cancer patients. Materials and Methods. 92 endometrial cancer patients, aged 37–84, were enrolled to our study. In all patients clinical stage, histologic grade, myometrial invasion, lymph node, and distant metastases were determined. Moreover, the survival time was assessed. Immunohistochemical analyses were performed on archive formalin fixed paraffin embedded tissue sections. Results. High significant differences (P = 0.0115) were reported between HIF-1α expression and the histologic subtype of cancer. Higher HIF-1α expression was associated with the higher risk of recurrence (P = 0.0434). The results of GLUT-1 and CAIX expression did not reveal any significant differences between the proteins expression in the primary tumor and the clinicopathological features. Conclusion. The important role of HIF-1α in the group of patients with the high risk of recurrence and the negative histologic subtype of the tumor suggest that the expression of this factor might be useful in the panel of accessory pathomorphological tests and could be helpful in establishing more accurate prognosis in endometrial cancer patients.

Delayed skin wound repair in proline-rich protein tyrosine kinase 2 knockout mice

Proline-rich protein tyrosine kinase 2 (Pyk2) is a member of the focal adhesion kinase family. We used Pyk2 knockout (Pyk2-KO) mice to study the role of Pyk2 in cutaneous wound repair. We report that the rate of wound closure was delayed in Pyk2-KO compared with control mice. To examine whether impaired wound healing of Pyk2-KO mice was caused by a keratinocyte cell-autonomous defect, the capacities of primary keratinocytes from Pyk2-KO and wild-type (WT) littermates to heal scratch wounds in vitro were compared. The rate of scratch wound repair was decreased in Pyk2-KO keratinocytes compared with WT cells. Moreover, cultured human epidermal keratinocytes overexpressing the dominant-negative mutant of Pyk2 failed to heal scratch wounds. Conversely, stimulation of Pyk2-dependent signaling via WT Pyk2 overexpression induced accelerated scratch wound closure and was associated with increased expression of matrix metalloproteinase (MMP)-1, MMP-9, and MMP-10. The Pyk2-stimulated increase in the rate of scratch wound repair was abolished by coexpression of the dominant-negative mutant of PKCδ and by GM-6001, a broad-spectrum inhibitor of MMP activity. These results suggest that Pyk2 is essential for skin wound reepithelialization in vivo and in vitro and that it regulates epidermal keratinocyte migration via a pathway that requires PKCδ and MMP functions.

Downregulation of CD9 in keratinocyte contributes to cell migration via upregulation of matrix metalloproteinase-9

Tetraspanin CD9 has been implicated in various cellular and physiological processes, including cell migration. In our previous study, we found that wound repair is delayed in CD9-null mice, suggesting that CD9 is critical for cutaneous wound healing. However, many cell types, including immune cells, endothelial cells, keratinocytes and fibroblasts undergo marked changes in gene expression and phenotype, leading to cell proliferation, migration and differentiation during wound repair, whether CD9 regulates kerationcytes migration directly remains unclear. In this study, we showed that the expression of CD9 was downregulated in migrating keratinocytes during wound repair in vivo and in vitro. Recombinant adenovirus vector for CD9 silencing or overexpressing was constructed and used to infect HaCaT cells. Using cell scratch wound assay and cell migration assay, we have also demonstrated that downregulation of CD9 promoted keratinocyte migration in vitro, whereas CD9 overexpression inhibited cell migration. Moreover, CD9 inversely regulated the activity and expression of MMP-9 in keratinocytes, which was involved in CD9-regulated keratinocyte migration. Importantly, CD9 silencing-activated JNK signaling was accompanied by the upregulation of MMP-9 activity and expression. Coincidentally, we found that SP600125, a JNK pathway inhibitor, decreased the activity and expression of MMP-9 of CD9-silenced HaCaT cells. Thus, our results suggest that CD9 is downregulated in migrating keratinocytes in vivo and in vitro, and a low level of CD9 promotes keratinocyte migration in vitro, in which the regulation of MMP-9 through the JNK pathway plays an important role.

News on microenvironmental physioxia to revisit skin cell targeting approaches

The skin is a multifunctional organ and a first line of defense actively protecting from environmental stress caused by injury, microbial treat, UV irradiation and environmental toxins. Diverse cutaneous cell types together with extracellular matrix elements and factors create a dynamic scene for cellular communication crucial in vital processes such as wound healing, inflammation, angiogenesis, immune response. Direct functional success of skin equilibrium depends on its microenvironment settings and particularly the local oxygen tension. Indeed, skin entire milieu is characterized by and highly dependent on its low oxygen tension called physioxia as emphasized in this review. In the context of skin physioxia, we review and propose here new approaches to minimize age-related changes in skin state and function. We particularly emphasize carbohydrate-mediated interactions and new 3D models of engineered skin substitutes. We highlight newly emerged tools and targets including stem cells, miRNAs, matrix metalloproteinases, mitochondria and natural antioxidants that are promising in prevention of skin ageing and disease restraint. In the era of advanced dermatology, new attempts are bringing us closer to 'well being' perception.

The biological behaviors of rat dermal fibroblasts can be inhibited by high levels of MMP9

Aims. To explore the effects of the high expression of MMP9 on biological behaviors of fibroblasts. Methods. High glucose and hyperhomocysteine were used to induce MMP9 expression in skin fibroblasts. Cell proliferation was detected by flow cytometry and cell viability by CCK-8. ELISA assay was used to detect collagen (hydroxyproline) secretion. Scratch test was employed to evaluate horizontal migration of cells and transwell method to evaluate vertical migration of cells. Results. The mRNA and protein expressions of MMP9 and its protease activity were significantly higher in cells treated with high glucose and hyperhomocysteine than those in control group. At the same time, the S-phase cell ratio, proliferation index, cell viability, collagen (hydroxyproline) secretion, horizontal migration rate, and the number of vertical migration cells decreased in high-glucose and hyperhomocysteine-treated group. Tissue inhibitor of metalloproteinase 1 (TIMP1), which inhibits the activity of MMP9, recovered the above biological behaviors. Conclusions. High expression of MMP9 in skin fibroblasts could be induced by cultureing in high glucose and hyperhomocysteine medium, which inhibited cell biological behaviors. Inhibitions could be reversed by TIMP1. The findings suggested that MMP9 deters the healing of diabetic foot ulcers by inhibiting the biological behaviors of fibroblasts.

Impairment of human keratinocyte mobility and proliferation by advanced glycation end products-modified BSA

The migration and proliferation of keratinocytes is critical to wound re-epithelialization and defects in this function are associated with the clinical phenomenon of chronic non-healing wounds. Advanced glycation end products (AGEs) occur through non-enzymatic glycation of long-lived proteins in diabetes and play important roles in diabetic complications. However, specific roles for AGEs in keratinocyte migration and proliferation, and the underlying molecular mechanisms, have not been fully established. The aim of the current study was to elucidate the interaction between AGE-modified bovine serum albumin (AGE-BSA) and keratinocytes. As a result, we found that AGE-BSA had no effect on the viability of keratinocytes for up to 48 h of incubation with 50 μg/ml of AGE-BSA. AGE-BSA (but not non-glycated BSA) exerted a concentration-dependent suppression of keratinocyte migration at a range of concentrations. The expression of matrix metalloproteinase-9 (MMP-9) was significantly up-regulated in keratinocytes incubated with increasing AGE-BSA, but tissue inhibitor of metalloproteinases-1 (TIMP-1) expression was down-regulated. AGE-BSA also profoundly depressed phospho-focal adhesion kinase-Tyr397 (p-FAK) and α2β1 integrin expression, while total-FAK expression levels remained constant, in keratinocytes. The proliferative capacity of keratinocytes was diminished after 72 h AGE-BSA incubation. Taken together, these findings suggested that in the presence of AGE-BSA, keratinocytes lose their migratory and proliferation abilities. These data also indicated that, in the context of the chronic hyperglycemia in diabetes, the effects of AGE-BSA on keratinocyte migration might be mediated through MMP-9/TIMP-1, p-FAK and α2β1 integrin.

Regulation of cell proliferation and migration by TAK1 via transcriptional control of von Hippel-Lindau tumor suppressor

Skin maintenance and healing after wounding requires complex epithelial-mesenchymal interactions purportedly mediated by growth factors and cytokines. We show here that, for wound healing, transforming growth factor-beta-activated kinase 1 (TAK1) in keratinocytes activates von Hippel-Lindau tumor suppressor expression, which in turn represses the expression of platelet-derived growth factor-B (PDGF-B), integrin beta1, and integrin beta5 via inhibition of the Sp1-mediated signaling pathway in the keratinocytes. The reduced production of PDGF-B leads to a paracrine-decreased expression of hepatocyte growth factor in the underlying fibroblasts. This TAK1 regulation of the double paracrine PDGF/hepatocyte growth factor signaling can regulate keratinocyte cell proliferation and is required for proper wound healing. Strikingly, TAK1 deficiency enhances cell migration. TAK1-deficient keratinocytes displayed lamellipodia formation with distinct microspike protrusion, associated with an elevated expression of integrins beta1 and beta5 and sustained activation of cdc42, Rac1, and RhoA. Our findings provide evidence for a novel homeostatic control of keratinocyte proliferation and migration mediated via TAK1 regulation of von Hippel-Lindau tumor suppressor. Dysfunctional regulation of TAK1 may contribute to the pathology of non-healing chronic inflammatory wounds and psoriasis.

Acrolein activates matrix metalloproteinases by increasing reactive oxygen species in macrophages

Acrolein is a ubiquitous component of environmental pollutants such as automobile exhaust, cigarette, wood, and coal smoke. It is also a natural constituent of several foods and is generated endogenously during inflammation or oxidation of unsaturated lipids. Because increased inflammation and episodic exposure to acrolein-rich pollutants such as traffic emissions or cigarette smoke have been linked to acute myocardial infarction, we examined the effects of acrolein on matrix metalloproteinases (MMPs), which destabilize atherosclerotic plaques. Our studies show that exposure to acrolein resulted in the secretion of MMP-9 from differentiated THP-1 macrophages. Acrolein-treatment of macrophages also led to an increase in reactive oxygen species (ROS), free intracellular calcium ([Ca2+](i)), and xanthine oxidase (XO) activity. ROS production was prevented by allopurinol, but not by rotenone or apocynin and by buffering changes in [Ca2+](I) with BAPTA-AM. The increase in MMP production was abolished by pre-treatment with the antioxidants Tiron and N-acetyl cysteine (NAC) or with the xanthine oxidase inhibitors allopurinol or oxypurinol. Finally, MMP activity was significantly stimulated in aortic sections from apoE-null mice containing advanced atherosclerotic lesions after exposure to acrolein ex vivo. These observations suggest that acrolein exposure results in MMP secretion from macrophages via a mechanism that involves an increase in [Ca2+](I), leading to xanthine oxidase activation and an increase in ROS production. ROS-dependent activation of MMPs by acrolein could destabilize atherosclerotic lesions during brief episodes of inflammation or pollutant exposure.

Mechanisms of adaptive angiogenesis to tissue hypoxia

Angiogenesis is mostly an adaptive response to tissue hypoxia, which occurs under a wide variety of situations ranging from embryonic development to tumor growth. In general, angiogenesis is dependent on the accumulation of hypoxia inducible factors (HIFs), which are heterodimeric transcription factors of alpha and beta subunits. Under normoxia, HIF heterodimers are not abundantly present due to oxygen dependent hydroxylation, polyubiquitination, and proteasomal degradation of alpha subunits. Under hypoxia, however, alpha subunits are stabilized and form heterodimers with HIF-1beta which is not subject to oxygen dependent regulation. The accumulation of HIFs under hypoxia allows them to activate the expression of many angiogenic genes and therefore initiates the angiogenic process. In recent years, however, it has become clear that various other mechanisms also participate in fine tuning angiogenesis. In this review, I discuss the relationship between hypoxia and angiogenesis under five topics: (1) regulation of HIF-alpha abundance and activity by oxygen tension and other conditions including oxygen independent mechanisms; (2) hypoxia-regulated expression of angiogenic molecules by HIFs and other transcription factors; (3) responses of vascular cells to hypoxia; (4) angiogenic phenotypes due to altered HIF signaling in mice; and (5) role of the HIF pathway in pathological angiogenesis. Studies discussed under these topics clearly indicate that while mechanisms of oxygen-regulated HIF-alpha stability provide exciting opportunities for the development of angiogenesis or anti-angiogenesis therapies, it is also highly important to consider various other mechanisms for the optimization of these procedures.