Exogenous nitric oxide enhances the synthesis of type I collagen and heat shock protein 47 by normal human dermal fibroblasts

Hormonal, immune, and oxidative stress responses to blood flow-restricted exercise

INTRODUCTION

Heavy-load free-flow resistance exercise (HL-FFRE) is a widely used training modality. Recently, low-load blood-flow restricted resistance exercise (LL-BFRRE) has gained attention in both athletic and clinical settings as an alternative when conventional HL-FFRE is contraindicated or not tolerated. LL-BFRRE has been shown to result in physiological adaptations in muscle and connective tissue that are comparable to those induced by HL-FFRE. The underlying mechanisms remain unclear; however, evidence suggests that LL-BFRRE involves elevated metabolic stress compared to conventional free-flow resistance exercise (FFRE).

AIM

The aim was to evaluate the initial (<10 min post-exercise), intermediate (10-20 min), and late (>30 min) hormonal, immune, and oxidative stress responses observed following acute sessions of LL-BFRRE compared to FFRE in healthy adults.

METHODS

A systematic literature search of randomized and non-randomized studies was conducted in PubMed, Embase, Cochrane Central, CINAHL, and SPORTDiscus. The Cochrane Risk of Bias (RoB2, ROBINS-1) and TESTEX were used to evaluate risk of bias and study quality. Data extractions were based on mean change within groups.

RESULTS

A total of 12525 hits were identified, of which 29 articles were included. LL-BFRRE demonstrated greater acute increases in growth hormone responses when compared to overall FFRE at intermediate (SMD 2.04; 95% CI 0.87, 3.22) and late (SMD 2.64; 95% CI 1.13, 4.16) post-exercise phases. LL-BFRRE also demonstrated greater increase in testosterone responses compared to late LL-FFRE.

CONCLUSION

These results indicate that LL-BFRRE can induce increased or similar hormone and immune responses compared to LL-FFRE and HL-FFRE along with attenuated oxidative stress responses compared to HL-FFRE.

Metabolic reprogramming of tumor-associated macrophages by collagen turnover promotes fibrosis in pancreatic cancer

A hallmark of pancreatic tumors is their highly desmoplastic stroma composed of fibroblasts, immune cells, and a dense network of collagen fibers. Tumor-associated macrophages are one of the most abundant immune cell populations in the pancreatic tumor stroma. Their protumorigenic function has been attributed predominantly to their capacity to promote immune evasion and metastasis. Tumor-assoc iated macrophages are also well known for their role in the remodeling of the stroma via collagen production and degradation, with the latter being mediated by mannose receptor (MRC1)-dependent endocytosis of collagen. Here we show that MRC1-mediated collagen internalization and subsequent lysosomal degradation by macrophages harboring a tumor-associated phenotype are accompanied by the accumulation of collagen-derived intracellular free amino acids and increased arginine biosynthesis. The resulting increase in intracellular arginine levels leads to the up-regulation of inducible nitric oxide synthase and the production of reactive nitrogen species. Furthermore, reactive nitrogen species derived from internalized and degraded collagen promotes a profibrotic phenotype in pancreatic stellate cells resulting in enhanced intratumoral collagen deposition. Overall, our findings identify a role for extracellular matrix remodeling in the functional modulation of tumor-associated macrophages via metabolic rewiring.

Salvianolic acid B regulates collagen synthesis: Indirect influence on human dermal fibroblasts through the microvascular endothelial cell pathway

BACKGROUND

Salvianolic acid B (SAB) is one of the main active ingredients of Salvia Miltiorrhiza. It has significant skin anti-aging, whitening, and sun protection properties.

AIMS

The study aimed at studying the mechanism underlying the effect of salvianolic acid Bon collagen synthesis, which has good anti-aging efficacy and modulates microcirculation.

METHODS

This study employed available public databases, bioinformatics methodologies, and the inverse docking approach to explore the effectiveness of SAB in the regulating collagen synthesis, and then used an human dermal fibroblast (HDF)- Human dermal microvascular endothelial cell (HDMEC) in vitro model to validate the predicted mechanism of SAB in influencing collagen synthesis.

RESULTS

The results showed that NO production in SAB-treated HDMEC-conditioned medium was increased compared to that in control media, and the same tendency was also observed for growth factor production. SAB also upregulated HDMEC cellular eNOS and VEGF. When SAB-treated HDMEC conditioned medium was transferred to HDFs, the expression of collagen I, collagen III, and elastin in HDFs was upregulated and MMP-1 was downregulated.

CONCLUSIONS

The results show that SAB regulates collagen through the HDMEC-HDF pathway. Furthermore, the mechanisms might be closely related to the microcirculation factors NO and VEGF.

Relationship Between Glycated Hemoglobin and Vibration Perception Threshold in Diabetic Peripheral Neuropathy

Foot ulcers, infections, and deformity are some of the major sources of mortality and morbidity among the diabetic population. The relationship between glycated hemoglobin (HbA1c) and diabetic peripheral neuropathy (DPN) has been well established. There is a dearth of literature on the relationship between vibration perception threshold (VPT) and HbA1c values. So, the objective of the study was to determine the strength of linear relationship between HbA1c levels and vibration perception threshold in DPN. This cross-sectional study was conducted at Kasturba Hospital, Manipal, and diabetic foot screening camps held at various parts of Udupi district. Ethical approval was obtained from the Institutional Ethics Committee, Kasturba Hospital, Manipal (IEC:281/2017). A total of 534 participants ranging from 30 to 70 years of age and were diagnosed with type 2 diabetes mellitus on medications were included in the study. Neuropathy assessment consisting of monofilament and vibration perception threshold was done using Neurotouch beta version (Yostra Labs, Bengaluru, India). HbA1c measurement was done using turbidimetric inhibition immunoassay technique (Roche Diagnostics, Mannheim, Germany). Pearson correlation coefficient showed a moderate to good correlation between HbA1c and VPT (r = .0.753, P < .001). Linear regression result has shown a significant relationship of VPT with HbA1c (4.033 [95% confidence interval = 3.67-4.39]). The present study has concluded that there is strong relationship between HbA1c values and VPT and could be a predictor for complications in the foot following DPN.

Cecropia obtusa extract and chlorogenic acid exhibit anti aging effect in human fibroblasts and keratinocytes cells exposed to UV radiation

Cecropia obtusa is popularly used in the Amazonian region and exhibits antioxidant activity. Cosmetic formulations containing C. obtusa extract are commercially available for purchase; however, the chemical composition and the effects of the topical application of the extract are not described in the literature. Therefore, this study aimed to identify the main components of C. obtusa for the first time and to assess the anti aging effect in human fibroblasts and keratinocytes exposed to UVR. The main components in C. obtusa extract were identified by LC-DAD-MS/MS as chlorogenic acid (CGA), luteolin-C-hexoside, luteolin-C-hexose-O-deoxy-hexose, and apigenin-C-hexose-O-deoxy-hexose. C. obtusa extract and CGA decreased the metalloproteinase-1 and protein carbonyl levels and increased the collagen and hyaluronic acid contents. Overall, the extract exhibited better activity than CGA, and we demonstrated the ability of the extract to protect against the UV-induced increase in the pro inflammatory cytokines IL-1β and IL-6, which are potential pathways of the antioxidant and anti aging effect. The chemical characterization added important data to broaden the knowledge related to C. obtusa, and the results suggest that the extract is a promising candidate to be incorporated in topical photochemoprotective formulations.

Nitric oxide: Is it the culprit for the continued expansion of keloids?

Keloids are characterized by excessive proliferation of fibroblasts and invasion of surrounding healthy skin. High levels of Nitric Oxide (NO) are thought to be the crucial factor within the micro-environment in promoting keloid formation. However, the effects and mechanisms of NO on the proliferation of Keloid Fibroblasts (KDFs) remain unclear. In this study, we investigated the effect of NO on KDFs proliferation by Sodium Nitroprusside (SNP), an NO donor. Our results show that SNP significantly enhanced KDFs proliferation. Moreover, with prolonged treatment with SNP after cell confluence, the growth of KDFs escape contact inhibition and experience significant pile up growth. Furthermore, PTIO, an NO scavenger, attenuated SNP-enhanced cell proliferation effectively. The mechanism involved in SNP-induced KDFs proliferation was soluble Guanylyl Cyclase (sGC) and cGMP independent. ODQ, a specific sGC inhibitor, failed to suppress SNP-enhanced KDFs proliferation. 8-Bromo-c GMP, a cell-permeable cGMP analogue, could not stimulate KDFs proliferation. Erk and Akt provide important signaling for cell growth. U0126 and LY294002, inhibitors of Erk and Akt respectively, block SNP-enhanced KDFs proliferation effectively. As expected, a Western blot showed that SNP up-regulated the phosphorylation levels of Erk and Akt. Moreover, it decreased the expression of p²⁷, a cell cycle inhibitor. Our results reveal that SNP induced KDFs proliferation and loss contact inhibition led to pile up growth via activation of the Erk and Akt pathways, as well as a decreased expression of p²⁷. Thus, we speculate that the pathological feature of continuous expansion in keloids is caused by NO-induced KDFs sustained growth.

Sonic hedgehog-c-Jun N-terminal kinase-zinc finger protein Gli1 signaling protects against high glucose concentration-induced reactive oxygen species generation in human fibroblasts

Diabetes mellitus (DM) complications affect patients and cause varying damage. Skin ulcers exhibit difficulties in wound healing, and the regulatory basis for this remains unclear. High glucose concentration (HG) was utilized to mimic DM in cultured cells. Reverse transcription-quantitative polymerase chain reaction, western blotting and fluorescence dye analyses were performed to analyze the effects of hedgehog signaling in regulation of HG or diabetes in fibroblasts. HG-stress suppressed hedgehog-signaling gene expression, whereas the apoptosis and inflammatory response markers, Caspase-3 and plasminogen activator inhibitor-1 (PAI1), respectively, were induced. In addition, HG-stress inhibited the fibroblast proliferation rate. In parallel, treatment with Sonic hedgehog (Shh), an activator of hedgehog signaling, together with HG eliminated effects of HG on expression of hedgehog-signaling genes, Caspase-3 and PAI1, and rescued the cell proliferation rate in fibroblasts. In addition, Shh application activated c-Jun N-terminal kinase (JNK), which was inhibited by HG stress. sp600125, a JNK specific inhibitor, treatment inhibited the effect of Shh on fibroblast proliferation and hedgehog-signaling marker gene expression. Furthermore, zinc finger protein Gli1 (Gli1) overexpression partially eliminated the effect of HG and sp600125 on fibroblast proliferation, and reduced HG-induced ROS generation in fibroblasts. Together, these results indicate that HG stress inhibits hedgehog signaling, and Shh-JNK-Gli1 pathway positively regulates HG-induced damage on fibroblasts.

Annexin A2 functions downstream of c‑Jun N‑terminal kinase to promote skin fibroblast cell migration

Delayed healing of skin wounds is one of the outcomes of diabetes mellitus (DM), a condition that affects a significant number of patients worldwide. However, the underlying mechanisms remain unknown. In order to examine proteome alterations in DM, a rat model of type 1 diabetes was developed using streptozotocin injections. The proteomic responses of normal and DM rat skin were analyzed by two‑dimensional electrophoresis, and differentially expressed proteins were identified using a liquid chromatography/mass spectrometry system. DM induced 36 and repressed 41 differentially expressed proteins, respectively. Altered proteins were involved in a number of biological processes, including RNA and protein metabolism, the tricarboxylic acid cycle, glycolysis, cytoskeleton regulation, hydrogen detoxification and calcium‑mediated signal transduction. In addition, overexpression of annexin A2, one of the signaling proteins altered by DM, accelerated the rate of human skin fibroblast cell migration. Application of SP600125, an inhibitor of a key regulator of cell migration c‑Jun N‑terminal kinase (JNK), inhibited the migration of normal cells. By contrast, SP600125 treatment did not inhibit the migration of annexin A2‑overexpressed cells, indicating that annexin A2 may function downstream of JNK. In conclusion, the results of the present study reveal the potential proteomic responses to DM in skin tissues, and demonstrate a positive functional role of annexin A2 in fibroblast cell migration.

Transcriptomic study of high‑glucose effects on human skin fibroblast cells

Skin ulcers are a common complication of diabetes mellitus (DM). Fibroblasts are located within the dermis of skin tissue and can be damaged by diabetes. However, the underlying mechanism of how DM affects fibroblasts remains elusive. To understand the effects of DM on fibroblasts, the current study mimicked DM by high‑glucose (HG) supplementation in the culture medium of human foreskin primary fibroblast cells, and the analysis of transcriptomic changes was conducted. RNA sequencing‑based transcriptome analysis identified that, upon HG stress, 463 genes were upregulated and 351 genes downregulated (>1.5‑fold changes; P<0.05). These altered genes were distributed into 20 different pathways. In addition, gene ontology (GO) analysis indicated that 31 GO terms were enriched. Among the pathways identified, nuclear factor κB (NF‑κB) pathway genes were highly expressed, and the addition of Bay11‑7082, a typical NF‑κB signaling inhibitor, blocked the previously observed alterations in plasminogen activator inhibitor 1 (PAI1), an inflammation marker and frizzled class receptor 8 (FZD8), a Wnt signaling gene, expression that resulted from HG stress. Furthermore, an inhibitor of Wnt signaling diminished the role of Bay11‑7082 in the regulation of PAI1 expression under HG conditions, suggesting that Wnt signaling may function downstream of the NF‑κB pathway to protect fibroblast cells from HG stress. To the best of our knowledge, the current study is the first analysis of transcriptomic responses under HG stress in human fibroblasts. The data provided here may aid the understanding of the molecular mechanisms by which fibroblast cells are damaged in the skin of patients with DM.

Layered silicate clay functionalized with amino acids: wound healing application

Laponite holds amino acid between its interlayer spaces and releases it in contact with wound fluid through ionic exchange process.

Evaluation of wound healing activity of ferulic acid in diabetic rats

In diabetic patients, there is impairment in angiogenesis, neovascularisation and failure in matrix metalloproteineases (MMPs), keratinocyte and fibroblast functions, which affects wound healing mechanism. Hence, diabetic patients are more prone to infections and ulcers, which finally result in gangrene. Ferulic acid (FA) is a natural antioxidant found in fruits and vegetables, such as tomatoes, rice bran and sweet corn. In this study, wound healing activity of FA was evaluated in streptozotocin-induced diabetic rats using excision wound model. FA-treated wounds were found to epithelise faster as compared with diabetic wound control group. The hydroxyproline and hexosamine content increased significantly when compared with diabetic wound control. FA effectively inhibited the lipid peroxidation and elevated the catalase, superoxide dismutase, glutathione and nitric oxide levels along with the increase in the serum zinc and copper levels probably aiding the wound healing process. Hence, the results indicate that FA significantly promotes wound healing in diabetic rats.

Local delivery of nitric oxide: targeted delivery of therapeutics to bone and connective tissues

Non-invasive treatment of injuries and disorders affecting bone and connective tissue remains a significant challenge facing the medical community. A treatment route that has recently been proposed is nitric oxide (NO) therapy. Nitric oxide plays several important roles in physiology with many conditions lacking adequate levels of NO. As NO is a radical, localized delivery via NO donors is essential to promoting biological activity. Herein, we review current literature related to therapeutic NO delivery in the treatment of bone, skin and tendon repair.

Biologic activities of molecular chaperones and pharmacologic chaperone imidazole-containing dipeptide-based compounds: natural skin care help and the ultimate challenge: implication for adaptive responses in the skin

Accumulation of molecular damage and increased molecular heterogeneity are hallmarks of photoaged skin and pathogenesis of human cutaneous disease. Growing evidence demonstrates the ability of molecular chaperone proteins and of pharmacologic chaperones to decrease the environmental stress and ameliorate the oxidation stress-related and glycation disease phenotypes, suggesting that the field of chaperone therapy might hold novel treatments for skin diseases and aging. In this review, we examine the evidence suggesting a role for molecular chaperone proteins in the skin and their inducer and protecting agents: pharmacologic chaperone imidazole dipeptide-based agents (carcinine and related compounds) in cosmetics and dermatology. Furthermore, we discuss the use of chaperone therapy for the treatment of skin photoaging diseases and other skin pathologies that have a component of increased glycation and/or free radical-induced oxidation in their genesis. We examine biologic activities of molecular and pharmacologic chaperones, including strategies for identifying potential chaperone compounds and for experimentally demonstrating chaperone activity in in vitro and in vivo models of human skin disease. This allows the protein to function and traffic to the appropriate location in the skin, thereby increasing protein activity and cellular function and reducing stress on skin cells. The benefits of imidazole dipeptide antioxidants with transglycating activity (such as carcinine) in skin care are that they help protect and repair cell membrane damage and help retain youthful, younger-looking skin. All skin types will benefit from daily, topical application of pharmacologic chaperone antioxidants, anti-irritants, in combination with water-binding protein agents that work to mimic the structure and function of healthy skin. General strategies are presented addressing ground techniques to improve absorption of usually active chaperone proteins and dipeptide compounds, include encapsulation into hydrophobic carriers, a combination with penetration enhancers, active electrical transport, or chemical modification to increase hydrophobicity.

The effect of isosaponarin isolated from wasabi leaf on collagen synthesis in human fibroblasts and its underlying mechanism

Wasabi has been used as an important spice in Japanese foods. The wasabi leaves were used as a cosmetic material, but its biological activities have not yet been examined. We investigated the effect of isosaponarin derived from wasabi leaf on collagen synthesis in human fibroblasts. The production of type I collagen in human fibroblasts was increased with treatment of wasabi leaf extract. Isosaponarin isolated from wasabi leaves belonged to the group of flavone glycoside, and was the key compound in collagen synthesis from the wasabi leaf ingredients. Isosaponarin increased the type I collagen production at the mRNA gene level. The treatment of isosaponarin did not influence the production of transforming growth factor-beta (TGF-beta) protein, but increased the production of TGF-beta type II receptor (TbetaR-II) protein and TbetaR-II mRNA. Prolyl 4-hydroxylase (P4H) protein and P4H mRNA were increased by treatment with isosaponarin. Heat shock protein 47 (HSP47) was not increased by treatment with isosaponarin. These results suggested that isosaponarin increased collagen synthesis in human fibroblasts, caused by up-regulated TbetaR-II and P4H production.

Role of antioxidants in the skin: anti-aging effects

Intracellular and extracellular oxidative stress initiated by reactive oxygen species (ROS) advance skin aging, which is characterized by wrinkles and atypical pigmentation. Because UV enhances ROS generation in cells, skin aging is usually discussed in relation to UV exposure. The use of antioxidants is an effective approach to prevent symptoms related to photo-induced aging of the skin. In this review, the mechanisms of ROS generation and ROS elimination in the body are summarized. The effects of ROS generated in the skin and the roles of ROS in altering the skin are also discussed. In addition, the effects of representative antioxidants on the skin are summarized with a focus on skin aging.

Effect of bone morphogenetic protein-12 gene transfer on posterior cruciate ligament healing in a rabbit model

BACKGROUND

The posterior cruciate ligament heals to some extent after injury. However, results after conservative treatment may diminish with long-term follow-up. Bone morphogenetic protein-12 can induce formation of ligament tissues.

HYPOTHESIS

Bone morphogenetic protein-12 gene transfer can improve the histologic and biomechanical properties of healing posterior cruciate ligaments.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bilateral posterior cruciate ligaments of 32 rabbits were injured. The cut ends in 1 limb received an injection containing 3 x 10(7) pfu recombinant bone morphogenetic protein-12 adenovirus, and the posterior cruciate ligament in the contralateral limb served as an untreated control. Eight rabbits were sacrificed at each time point of 3, 6, 12, and 26 weeks after the operation. In addition, 6 rabbits receiving a sham operation were used to obtain normal control data. The posterior cruciate ligament specimens were evaluated biomechanically and histologically.

RESULTS

The repair tissue of the treatment group at 26 weeks was similar to the normal posterior cruciate ligament in collagen arrangement, collagen formation, and mechanical properties. At weeks 6, 12, and 26, the ultimate load, stiffness, and energy absorbed at failure of the treatment group were significantly greater than those of the untreated group.

CONCLUSION

Adenovirus-mediated bone morphogenetic protein-12 gene transfer in a partial posterior cruciate ligament laceration rabbit model resulted in an obvious improvement of histologic properties, tensile strength, and stiffness of the repaired ligaments, indicating improved posterior cruciate ligament healing.

CLINICAL RELEVANCE

Bone morphogenetic protein-12 gene transfer is a potential future strategy to improve the repair of injured posterior cruciate ligaments.

Regulation of angiotensin II receptors and extracellular matrix turnover in human retinal pigment epithelium: role of angiotensin II

The early stage of age-related macular degeneration (AMD) is characterized by the formation of subretinal pigment epithelium (RPE) deposits as a result of the dysregulation in the turnover of extracellular matrix (ECM) molecules. However, the mechanism involved remains unclear. Hypertension (HTN) is an important risk factor for AMD, and angiotensin II (ANG II) is the most important hormone associated with HTN. However, the relevance of ANG II receptors and ANG II effects on RPE have not been investigated yet. Therefore, the expression and regulation of ANG II receptors as well as the ECM turnover were studied in human RPE. ANG II receptors were expressed and upregulated by ANG II in human RPE. This regulation resulted in functional receptor expression, since an increase in intracellular concentration of calcium was observed upon ANG II stimulation. ANG II also increased matrix metalloproteinase (MMP)-2 activity and MMP-14 at the mRNA and protein levels as well as type IV collagen degradation. These ANG II effects were abolished in the presence of the ANG II receptor subtype 1 (AT1) receptor antagonist candesartan. In contrast, ANG II decreased type IV collagen via both AT1 and AT2 receptors, suggesting a synergistic effect of the two receptor subtypes. In conclusion, we have confirmed the presence of ANG II receptors in human RPE and their regulation by ANG II as well as the regulation of ECM molecules via ANG II receptors. Our data support the hypothesis that ANG II may exert biological function in RPE through ANG II receptors and that ANG II may cause dysregulation of molecules that play a major role in the turnover of ECM in RPE basement membrane and Bruch's membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.

Regulation of angiotensin II receptors and extracellular matrix turnover in human retinal pigment epithelium: role of angiotensin II

The early stage of age-related macular degeneration (AMD) is characterized by the formation of subretinal pigment epithelium (RPE) deposits as a result of the dysregulation in the turnover of extracellular matrix (ECM) molecules. However, the mechanism involved remains unclear. Hypertension (HTN) is an important risk factor for AMD, and angiotensin II (ANG II) is the most important hormone associated with HTN. However, the relevance of ANG II receptors and ANG II effects on RPE have not been investigated yet. Therefore, the expression and regulation of ANG II receptors as well as the ECM turnover were studied in human RPE. ANG II receptors were expressed and upregulated by ANG II in human RPE. This regulation resulted in functional receptor expression, since an increase in intracellular concentration of calcium was observed upon ANG II stimulation. ANG II also increased matrix metalloproteinase (MMP)-2 activity and MMP-14 at the mRNA and protein levels as well as type IV collagen degradation. These ANG II effects were abolished in the presence of the ANG II receptor subtype 1 (AT1) receptor antagonist candesartan. In contrast, ANG II decreased type IV collagen via both AT1 and AT2 receptors, suggesting a synergistic effect of the two receptor subtypes. In conclusion, we have confirmed the presence of ANG II receptors in human RPE and their regulation by ANG II as well as the regulation of ECM molecules via ANG II receptors. Our data support the hypothesis that ANG II may exert biological function in RPE through ANG II receptors and that ANG II may cause dysregulation of molecules that play a major role in the turnover of ECM in RPE basement membrane and Bruch's membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.

Comparison of the effects of serpin A1, a recombinant serpin A1-IGF chimera and serpin A1 C-terminal peptide on wound healing

Serpin A1 (alpha1-antitrypsin, alpha1-proteinase inhibitor), a potent neutrophil elastase inhibitor, has therapeutic potential as a wound-healing agent. We compared the in vitro wound-healing action of serpin A1-IGF, a recombinant fusion protein of serpin A1(M351E-M358L) and insulin-like growth factor I with that observed in the presence of natural serpin A1 or A1-C26, the synthetic C-terminal 26 residue peptide of serpin A1, previously shown to have mitogenic and antiviral activities. All agents reduced wound sizes in monolayers of the kidney epithelial cell line LLC-PK1 and in primary cultures of human skin fibroblasts. Wound reduction in primary human keratinocytes was only observed with the serpin A1-IGF chimera. None of the factors stimulated cell proliferation using a colorimetric assay, with the exception of the serpin A1-IGF chimera, which caused a significant increase of cell proliferation and thymidine incorporation in human skin fibroblasts. However, wound healing by the A1-IGF chimera was reduced in keratinocytes in the presence of mitomycin C, suggesting a role of cell proliferation in wound reduction. The hydrophobic A1-C26 peptide significantly increased the production of collagen I in skin fibroblasts, an appealing asset for skin care applications.

Osteogenic differentiation of human mesenchymal bone marrow cells in silk scaffolds is regulated by nitric oxide

Bone marrow-derived mesenchymal stem cells (BMSC) are a powerful tool for tissue engineering and can be used in the regeneration of bone and other tissues. Nitric oxide (NO) produced by the endothelial NO synthase (eNOS) plays an important role in bone development and healing. We hypothesized that NO plays a role in osteogenic differentiation of BMSC cultured in three-dimensional silk scaffolds. eNOS protein was measured by Western Analysis and its activity was assessed by measuring nitrite in culture supernatants. Mineralization was evaluated through calcium deposition and the expression of genes associated with osteogenic differentiation (collagen I, RUNX2, and osteocalcin) was quantified using real-time RT-PCR. eNOS was consistently expressed with minor fluctuations, but NO production significantly increased at later time points (weeks 4 and 5). Addition of a competitive NOS inhibitor (L-NAME) resulted in a modest decrease in calcium deposition, which became statistically significant in week 5. This was preceded by a dramatic decrease in RUNX2 and osteocalcin expression in week 4. These results support our hypothesis and implicate NO as an important player in bone tissue engineering.

Involvement of protein kinase A in nitric oxide stimulating effect on a BK(Ca) channel of human dermal fibroblasts

We reported previously that a large-conductance Ca2+-activated K+ (BK(Ca)) channel constitutes a significant fraction of the K+ current in human dermal fibroblasts, and that nitric oxide (NO) increases the open-channel probability (NPo) of BK(Ca) channels via a soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) pathway. The purpose of this study was to investigate whether the adenylate cyclase (AC)/cAMP/protein kinase A (PKA) pathway may also be involved in NO action on BK(Ca) channels in human dermal fibroblasts. Electrophysiological single-channel recordings were performed on fifth-passage cells of human penile skin cultures. KT5720 (specific PKA inhibitor) blocked the stimulatory effect of sodium nitroprusside (NO donor) on BK(Ca) channels. By contrast, forskolin (AC activator) or 8-bromo-cAMP (cell-permeable cAMP analog) did not increase the NPo of the channel. The PKA catalytic subunit (PKAcs) alone did not increase the NPo of the channel in cell-attached and inside-out patches, however, PKAcs with cGMP increased the NPo. In contrast, PKAcs with cGMP did not increase the NPo of BK(Ca) channels with 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one pretreatment, and KT5720 pretreatment also blocked the stimulatory effect of 8-Br-cGMP. In conclusion, the present data suggest the involvement of PKA in the stimulatory effect of NO on the BK(Ca) channel in human dermal fibroblasts through cGMP.

Nitric oxide in the pathogenesis of diffuse pulmonary fibrosis

By studying the responses of nitric oxide in pulmonary fibrosis, the role of inducible nitric oxide synthase in diffuse pulmonary fibrosis as caused by lipopolysaccharide (LPS) treatment was investigated. When compared to rats treated with LPS only, the rats pretreated with 1400W (an iNOS-specific inhibitor) were found to exhibit a reduced level in: (i) NOx (nitrate/nitrite) production, (ii) collagen type I protein expression, (iv) soluble collagen production, and (iv) the loss of body weight and carotid artery PO2. In the pulmonary fibroblast culture, exogenous NO from LPS-stimulated secretion by macrophages or from a NO donor, such as DETA NONOate, was observed to induce the expression of TIMP-1, HSP47, TGF-beta1, and collagen type I as well as the phosphorylation of SMAD-2. After inhalation of NO for 24 h, an up-regulation of collagen type I protein was also noted to occur in rat pulmonary tissue. The results suggest that the NO signal pathway enhanced the expression of TGF-beta1, TIMP-1, and HSP47 in pulmonary fibroblasts, which collectively demonstrate that the NO signal pathway could activate the SMAD-signal cascade, by initiating a rapid increase in TGF-beta1, thereby increasing the expression of TIMP-1 and HSP47 in pulmonary fibroblasts, and play an important role in pulmonary fibrosis.

Induction of TIMP-1 and HSP47 synthesis in primary keloid fibroblasts by exogenous nitric oxide

BACKGROUND

The excessive accumulation of extracellular matrix is a hallmark of many fibrotic diseases, including the hypertrophic scar and keloid. Recent reports from this research team had shown that exogenous nitric oxide (NO) participates in the keloid formation; however, its role on the synthesis of fibrotic factor (TGF-beta1, TIMP-1 and HSP47) in the keloid fibroblasts (KF) remained unclear.

OBJECTIVE

In this study, to better define the potential effect of exogenous NO on the expression of fibrotic factors in KF, the enhancing effect of exogenous NO, released from a NO donor, on the synthesis of fibrotic factors in KF was investigated.

METHODS

The seven primary KF cultures were set up to measure the effect of exogenous NO on enhancing the expression of fibrotic factor.

RESULTS

Elevation of cellular cGMP levels was observed to be induced by NO or blocked by the hydrolysis activity of phosphodiesterase (PDE) by the PDE inhibitor. The elevated levels of cellular cGMP were noted to enhance the expression of TIMP-1 and HSP47 in KF. Exogenous NO was found to significantly accelerate the production of TIMP-1 and HSP47 in the seven primary KFs with a corresponding increase in the production of TGF-beta1.

CONCLUSION

The results have led to a conclusion, that is: the excess collagen formations in the keloid lesion may be attributed to the NO/cGMP signal pathway by initiating a rapid increase in the expression of TGF-beta1, TIMP-1 and HSP47 in the KF cells.

Gene activation by bioactive glasses

Bioactive glasses have been shown to regulate gene expression in both hard and soft tissue repair. New resorbable bioactive glass constructs are now being developed that can influence gene expression in the local environment by manipulating material properties such as the surface chemistry, topography and the release of dissolution ions. The success of these scaffolds, however, may depend upon a greater understanding of the bioactive glass stimulated gene expression pathways. This will allow the construction of tissue specific scaffolds with tailored surface chemistry, topography and ion release rates. This paper summarises the advances made in understanding gene expression in response to bioactive glasses and discusses the future steps required for further insights into these molecular mechanisms.