In Situ Photo-crosslinkable Hyaluronic Acid/Gelatin Hydrogel for Local Nitric Oxide Delivery.

An increasing number of studies have shown that the local release of nitric oxide (NO) from hydrogels stimulates tissue regeneration by modulating cell proliferation, angiogenesis, and inflammation. The potential biomedical uses of NO-releasing hydrogels can be expanded by enabling their application in a fluid state, followed by controlled gelation triggered by an external factor. In this study, we engineered a hydrogel composed of methacrylated hyaluronic acid (HAGMA) and thiolated gelatin (GELSH) with the capacity for in situ photo-cross-linking, coupled with localized NO release. To ensure a gradual and sustained NO release, we charged the hydrogels with poly(l-lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with S-nitrosoglutathione (GSNO), safeguarding SNO group integrity during photo-cross-linking. The formation of thiol-ene bonds via the reaction between GELSH's thiol groups and HAGMA's vinyl groups substantially accelerated gelation (by a factor of 6) and increased the elastic modulus of hydrated hydrogels (by 1.9-2.4 times). HAGMA/GELSH hydrogels consistently released NO over a 14 day duration, with the release of NO depending on the hydrogels' equilibrium swelling degree, determined by the GELSH-to-HAGMA ratio. Biocompatibility assessments confirmed the suitability of these hydrogels for biological applications as they display low cytotoxicity and stimulated fibroblast adhesion and proliferation. In conclusion, in situ photo-cross-linkable HAGMA/GELSH hydrogels, loaded with PLGA-GSNO nanoparticles, present a promising avenue for achieving localized and sustained NO delivery in tissue regeneration applications.

Photocurable Nitric Oxide-Releasing Copolyester for the 3D Printing of Bioresorbable Vascular Stents.

The design of bioresorbable vascular stents (BVS) capable of releasing nitric oxide (NO) at the implant site may enable BVS to mimic the antiplatelet, antiproliferative, and pro-endothelial actions of NO, overcoming complications of BVS such as late thrombosis and restenosis. In this study, the fabrication of BVS composed of methacrylated poly(dodecanediol citrate-co-dodecanediol S-nitroso-mercaptosuccinate) (mP(DC-co-DMSNO)), a novel elastomeric, bioabsorbable, and photocurable copolyester, containing covalently bound S-nitrosothiol groups in the carbon backbone of the polymer, is reported. The mP(DC-co-DMSNO) stents are manufactured via photoinduced 3D printing and allow deployment via a self-expansion process from a balloon catheter. After deployment, hydration of the stents triggers the release of NO, which is maintained during the slow hydrolysis of the polymer. Real-time NO release measurements show that by varying the copolyester composition and the strut geometry of the mP(DC-co-DMSNO) stents, it is possible to modulate their NO release rate in the range of 30-52 pmol min-1 cm-2 . Preliminary biological assays in cell culture show that endothelial cells adhere to the surface of the stents and that NO release favors their endothelization. Thus, mP(DC-co-DMSNO) may emerge as a new platform for the fabrication of advanced BVS.

Nitric Oxide-Releasing Supramolecular Cellulose Nanocrystal/Silsesquioxane Foams.

Cellulose nanocrystals (CNC)-based foams are promising tissue engineering materials that may facilitate implant-tissue integration and allow localized and controlled drug delivery. Herein, hybrid CNC-based foams, which are ultralightweight (30-100 mg cm-3 ), highly porous (>95%), ominiphilic and superabsorbent (1500-3000 wt% of water and/or toluene uptake) are obtained by the in situ condensation of poly(ethylene glycol) ditriethoxysilyl (TES-PEG-TES) into a 3D network, where silsesquioxane nanoparticles (SS-NP) are the crosslinking nodes, and CNC are entrapped forming ionic interactions, in a supramolecular structure. In a new approach, using 3-mercaptopropyltrimethoxysilane, sulfhydryl groups are inserted on the SS-NP periphery and S-nitrosated to enable the functionalization of SS-NP with S-nitrosothiol groups, which can nitric oxide (NO), in a process triggered by the hydration of the foams and modulated by their supramolecular structure. CNC-SS-PEG foams exhibit elevated thermal and structural stability, compressive strength compatible with various soft human tissues, and NO release rates (1-18 pmol mg-1 min-1 ) within the range of the beneficial NO actions. Thus, the CNC-SS-PEG foams herein described represent a new platform of supramolecular hybrid materials for localized delivery of NO, with potential uses in tissue engineering and other biomedical applications.

3D printed nitric oxide-releasing poly(acrylic acid)/F127/cellulose nanocrystal hydrogels.

Hydrogels have been used as matrices for the topical delivery of nitric oxide (NO) for achieving vasodilation, wound healing and analgesic actions. More recently, supramolecular hydrogels comprised of poly(acrylic acid) (PAA) and micellar Pluronic F127 (F127), prepared by thermal reaction, emerged as a suitable matrix for the incorporation of hydrophilic NO donors, such as S-nitrosoglutathione (GSNO). Herein, we describe an innovative method for the three-dimensional (3D) printing of cellulose nanocrystal (CNC)-containing and semi-interpenetrating PAA/F127 hydrogels by PAA photopolymerization via digital light processing (DLP), in the absence of organic solvents. Scanning electron microscopy showed that, differently from typical porous PAA-based hydrogels, the 3D printed PAA/F127/CNC hydrogels have dense morphology. By using transmission electron microscopy we confirmed for the first time the presence of F127 micelles in the printable resin, and their preservation after the photopolymerization process. The F127 micelles conferred compressive recoverability to the 3D printed PAA/F127/CNC hydrogels, widening their potential applications as soft biomaterials. PAA/F127/CNC hydrogels charged with GSNO are shown to release NO spontaneously upon hydration at initial rates that depend on the GSNO charge and are higher in the presence of CNC. As local NO release may exert cell proliferation action, 3D printed PAA/F127/CNC/GSNO hydrogels may serve as a versatile soft biomaterial for local NO delivery in regenerative medicine and other biomedical applications.

Visualization of supramolecular structure of Pluronic F127 micellar hydrogels using cryo-TEM.

Pluronic® F127 micellar hydrogels are of growing interest to the biomedical field due to their versatility as drug delivery systems. Pluronic® F127 is a symmetric and amphiphilic triblock copolymer which in aqueous medium self-assembles into micelles that pack togetherwith increasing temperature or concentration, leading to non-flowable hydrogels. The microstructure of these hydrogels is usually investigated by small-angle X-ray scattering, which is not a readily available technique. Conversely, cryo-TEM is a widespread technique used for investigating the morphology of aqueous systems. In the case of Pluronic® F127 micellar systems, the elevated viscosity poses a significant challenge for specimen preparation and, consequently, for cryo-TEM observation. Herein, we show a trustworthy, inexpensive and readily available methodology for preparing specimens of highly viscous micellar solutions and non-flowable hydrogels using an automated vitrification system. With this methodology we were able to visualize not only the morphology of individual Pluronic® F127 micelles -but also the supramolecular structure evolution as a function of concentration. This methodology opens up a wide range of opportunities for hydrogel characterization, although additional systematic studies might be required in order to optimize and replicate it for similar systems.

S-nitrosothiol-terminated Pluronic F127: Influence of microstructure on nitric oxide release.

HYPOTHESIS: Nitric oxide (NO)-releasing Pluronic F127 hydrogels (F127) containing dissolved S-nitrosothiols or pendant N-diazeniumdiolate (NONOate) groups have been described. The NO charging of these hydrogels is usually limited by their low stability or disruption of the micellar packing. S-nitrosothiol-terminated F127 may emerge as a new strategy for allowing NO delivery at different rates in biomedical applications. EXPERIMENTS: Terminal hydroxyl groups of F127 were esterified and reduced to produce F127-mercaptopropionate (HS-F127-SH), which was subsequently S-nitrosated to generate S-nitrosothiol-terminated F127 (ONS-F127-SNO). Micro-differential scanning calorimetry, 1H NMR spin-spin relaxation (T2), temperature-dependent small-angle X-ray scattering, and cryo-transmission electron microscopy, were used to determine the micellar packing structure, while real-time chemiluminescence NO detection and UV-Vis spectrophotometry were used to evaluate the kinetics of NO release. FINDINGS: HS-F127-SH micellization and gelation processes were analogous to native F127, however, with a decreased short-range ordering of the micelles. ONS-F127-SNO hydrogels released NO thorough a preferentially intramicellar SNO dimerization reaction. Increasing ONS-F127-SNO concentration reduces the rate of SNO dimerization and increases the overall rate of NO release to the gas phase, opening up new possibilities for tailoring NO delivery from F127-based hydrogels.

Wound healing action of nitric oxide-releasing self-expandable collagen sponge.

Mounting evidence showing that local nitric oxide (NO) delivery may significantly improve the wound healing process has stimulated the development of wound dressings capable of releasing NO topically. Herein, we describe the preparation of a self-expandable NO-releasing hydrolyzed collagen sponge (CS), charged with the endogenously found NO donor, S-nitrosoglutathione (GSNO). We show that cold pressed and GSNO-charged CS (CS/GSNO) undergo self-expansion to its original 3D shape upon water absorption to a swelling degree of 2,300 wt%, triggering the release of free NO. Topical application of compressed CS/GSNO on wounds in an animal model showed that exudate absorption by CS/GSNO leads to the release of higher NO doses during the inflammatory phase and progressively lower NO doses at later stages of the healing process. Moreover, treated animals showed significant increase in the mRNA expression levels of monocyte chemoattractant protein-1 (MCP-1), murine macrophage marker (F4/80), transforming growth factor beta (TGF-ß), stromal cell-derived factor 1 (SDF-1), insulin-like growth factor-1 (IGF-1), nitric oxide synthase(iNOS), and matrix metalloproteinase(MMP-9). Cluster differentiation 31 (CD31), vascular endothelial growth factor (VEGF), and F4/80 were measured on Days 7 and 12 by immunohistochemistry in the cicatricial tissue. These results indicate that the topical delivery of NO enhances the migration and infiltration of leucocytes, macrophages, and keratinocytes to the wounded tissue, as well as the neovascularization and collagen deposition, which are correlated with an accelerated wound closure. Thus, self-expandable CS/GSNO may represent a novel biocompatible and active wound dress for the topical delivery of NO on wounds.

S-nitrosothiol-terminated poly(vinyl alcohol): Nitric oxide release and skin blood flow response.

Polymeric biomaterials capable of delivering nitric oxide (NO) topically can be used to enhance skin blood flow (SkBF) and accelerate wound healing. Herein, we used reversible addition-fragmentation chain transfer radical (RAFT) polymerization to synthesize the first poly(vinyl alcohol) (PVA) functionalized with terminal NO-releasing S-nitrosothiol (RSNO) groups for topical NO delivery. This strategy was based on the synthesis of a precursor amino-terminated PVA (PVA-NH2), which was next functionalized with iminothiolane yielding 4-imino-4-amino-PVA-butane-1-thiol (PVA-SH), and finally S-nitrosated yielding S-nitroso 4-imino-4-amino-PVA-butane-1-thiol (PVA-SNO). Real-time chemiluminescence NO detection showed that blended films of pure PVA with PVA-SNO with mass ratios 30:70, 50:50 and 70:30 release NO with initial rates ranging from 1 to 12 nmol g-1 min-1, and lead to a 2 to 10-fold dose-response increase in the SkBF, after topical application on the ventral forearm of volunteers. These results show that PVA-SNO is a potential platform for topical NO delivery in biomedical applications.

Preparation of Organic Nitrates from Aryldiazoacetates and Fe(NO3)3·9H2O.

A thermal protocol is reported for the formal insertion of nitric acid into aryldiazoacetates using Fe(NO3)3·9H2O. This strategy is mild and high yielding and allows the preparation of a large variety of members of an unprecedented family of organic nitrates. The nitrate group can be also readily transformed into other functional groups and heterocyclic moieties and can possibly allow new biological explorations of untapped potential associated with their NO-releasing ability.

Influence of Pluronic F127 microenvironments on the photochemical nitric oxide release from S-nitrosoglutathione.

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) (F127) hydrogels have been used to deliver nitric oxide (NO) topically in biomedical applications. Here, the effect of F127 microenvironments on the photochemical NO release from S-nitrosoglutathione (GSNO) was investigated in F127 solutions 7.6 wt% 15 wt% and 22.5 wt% at 15 °C and 37 °C. Small-angle X-ray Scattering (SAXS) and Differential Scanning Calorimetry (DSC) measurements, along with proton Nuclear Magnetic Resonance (1H NMR) spectral shifts and T2 relaxation data at six different concentration-temperature conditions, allowed identifying F127 microphases characterized by: a sol phase of unimers; micelles in non-defined periodic order, and a gel phase of cubic packed micelles. Kinetic measurements showed that GSNO photodecompositon proceeds faster in micellized F127 where GSNO is segregated to the intermicellar microenvironment. Real time kinetic monitoring of NO release and T2 relaxation profiles showed that NO is preferentially partitioned into the hydrophobic PPO cores of the F127 micelles, with the consequent decrease in its rate of release to the gas phase. These results show that F127 microphases affect both the kinetics of GSNO photodecomposition and the rate of NO escape and can be used to modulate the photochemical NO delivery from F127/GSNO solutions.

Supramolecular poly(acrylic acid)/F127 hydrogel with hydration-controlled nitric oxide release for enhancing wound healing.

Topical nitric oxide (NO) delivery has been shown to accelerate wound healing. However, delivering NO to wounds at appropriate rates and doses requires new biomaterial-based strategies. Here, we describe the development of supramolecular interpolymer complex hydrogels comprising PEO-PPO-PEO (F127) micelles embedded in a poly(acrylic acid) (PAA) matrix, with S-nitrosoglutathione (GSNO) molecules dissolved in the hydrophilic domain. We show that PAA:F127/GSNO hydrogels start releasing NO upon hydration at rates controlled by their rates of water absorption. SAXS measurements indicate that the supramolecular structure of the hydrogels retains long-range order domains of F127 micelles. The PAA/F1227 hydrogels displayed dense morphologies and reduced rates of hydration. The NO release rates remain constant over the first 200 min, are directly correlated with the hydration rates of the PAA:F127/GSNO hydrogels, and can be modulated in the range of 40 nmol/g h to 1.5 µmol/g h by changing the PAA:F127 mass ratio. Long-term NO-release profiles over 5 days are governed by the first-order exponential decay of GSNO, with half-lives in the range of 0.5-3.4 days. A preliminary in vivo study on full-thickness excisional wounds in mice showed that topical NO release from the PAA:F127/GSNO hydrogels is triggered by exudate absorption and leads to increased angiogenesis and collagen fiber organization, as well as TGF-ß, IGF-1, SDF-1, and IL-10 gene expressions in the cicatricial tissue. In summary, these results suggest that hydration-controlled NO release from topical PAA:F127/GSNO hydrogels is a potential strategy for enhancing wound healing. STATEMENT OF SIGNIFICANCE: The topical delivery of nitric oxide (NO) to wounds may provide significant beneficial results and represent a promising strategy to treat chronic wounds. However, wound dressings capable of releasing NO after application and allowing the modulation of NO release rates, demand new platforms. Here, we describe a novel strategy to overcome these challenges, based on the use of supramolecular poly(acrylic acid) (PAA):F127 hydrogels charged with the NO donor S-nitrosoglutathione (GSNO) from whereby the NO release can be triggered by exudate absorption and delivered to the wound at rates controlled by the PAA:F127 mass ratio. Preliminary in vivo results offer a proof of concept for this strategy by demonstrating increased angiogenesis; collagen fibers organization; and TGF-ß, IGF-1, SDF-1, and IL-10 gene expressions in the cicatricial tissue after topical treatment with a PAA:F127/GSNO hydrogel.

Enzyme Prodrug Therapy Engineered into Electrospun Fibers with Embedded Liposomes for Controlled, Localized Synthesis of Therapeutics.

Enzyme prodrug therapy (EPT) enables localized conversion of inert prodrugs to active drugs by enzymes. Performance of EPT necessitates that the enzyme remains active throughout the time frame of the envisioned therapeutic application. ß-glucuronidase is an enzyme with historically validated performance in EPT, however it retains its activity in biomaterials for an insufficiently long period of time, typically not exceeding 7 d. Herein, the encapsulation of ß-glucuronidase in liposomal subcompartments within poly(vinyl alcohol) electrospun fibers is reported, leading to the assembly of biocatalytically active materials with activity of the enzyme sustained over at least seven weeks. It is further shown that liposomes provide the highly beneficial stabilization of the enzyme when incubated in cell culture media. The assembled biocatalytic materials successfully produce antiproliferative drugs (SN-38) using externally administered prodrugs (SN-38-glucuronide) and effectively suppress cell proliferation, with envisioned utility in the design of cardiovascular grafts.

Correction: Topical HPMC/S-Nitrosoglutathione Solution Decreases Inflammation and Bone Resorption in Experimental Periodontal Disease in Rats.

[This corrects the article DOI: 10.1371/journal.pone.0153716.].

Combined nitric oxide-releasing poly(vinyl alcohol) film/F127 hydrogel for accelerating wound healing.

Nitric oxide (NO) releasing biomaterials represent a potential strategy for use as active wound dressings capable of accelerating wound healing. Topical NO-releasing poly(vinyl alcohol) (PVA) films and Pluronic F127 hydrogels (F127) have already exhibited effective skin vasodilation and wound healing actions. In this study, we functionalized PVA films with SNO groups via esterification with a mixture of mercaptosucinic acid (MSA) and thiolactic acid (TLA) followed by S-nitrosation of the SH moieties. These films were combined with an underlying layer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), i.e., PEO-PPO-PEO (Pluronic F127) hydrogel and used for the topical treatment of skin lesions in an animal model. The mixed esterification of PVA with MSA and TLA led to chemically crosslinked PVA-SNO films with a high swelling capacity capable of spontaneously releasing NO. Real time NO-release measurements revealed that the hydrogel layer reduces the initial NO burst from the PVA-SNO films. We demonstrate that the combination of PVA-SNO films with F127 hydrogel accelerates wound contraction, decreases wound gap and cellular density and accelerates the inflammatory phase of the lesion. These results were reflected in an increase in myofibroblastic differentiation and collagen type III expression in the cicatricial tissue. Therefore, PVA-SNO films combined with F127 hydrogel may represent a new approach for active wound dressings capable of accelerating wound healing.

Nitric oxide released from luminal s-nitroso-N-acetylcysteine increases gastric mucosal blood flow.

Nitric oxide (NO)-mediated vasodilation plays a key role in gastric mucosal defense, and NO-donor drugs may protect against diseases associated with gastric mucosal blood flow (GMBF) deficiencies. In this study, we used the ex vivo gastric chamber method and Laser Doppler Flowmetry to characterize the effects of luminal aqueous NO-donor drug S-nitroso-N-acetylcysteine (SNAC) solution administration compared to aqueous NaNO2 and NaNO3 solutions (pH 7.4) on GMBF in Sprague-Dawley rats. SNAC solutions (600 µM and 12 mM) led to a rapid threefold increase in GMBF, which was maintained during the incubation of the solutions with the gastric mucosa, while NaNO2 or NaNO3 solutions (12 mM) did not affect GMBF. SNAC solutions (600 µM and 12 mM) spontaneously released NO at 37 °C at a constant rate of 0.3 or 14 nmol·mL-1·min-1, respectively, while NaNO2 (12 mM) released NO at a rate of 0.06 nmol·mL-1·min-1 and NaNO3 (12 mM) did not release NO. These results suggest that the SNAC-induced GMBF increase is due to their higher rates of spontaneous NO release compared to equimolar NaNO2 solutions. Taken together, our data indicate that oral SNAC administration is a potential approach for gastric acid-peptic disorder prevention and treatment.

S-nitrosoglutathione accelerates recovery from 5-fluorouracil-induced oral mucositis.

INTRODUCTION: Mucositis induced by anti-neoplastic drugs is an important, dose-limiting and costly side-effect of cancer therapy. AIM: To evaluate the effect of the topical application of S-nitrosoglutathione (GSNO), a nitric oxide donor, on 5-fluorouracil (5-FU)-induced oral mucositis in hamsters. MATERIALS AND METHODS: Oral mucositis was induced in male hamsters by two intraperitoneal administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) followed by mechanical trauma on the fourth day. Animals received saline, HPMC or HPMC/GSNO (0.1, 0.5 or 2.0 mM) 1 h prior to the 5-FU injection and twice a day for 10 or 14 days. Samples of cheek pouches were harvested for: histopathological analysis, TNF-α and IL-1ß levels, immunohistochemical staining for iNOS, TNF-α, IL-1ß, Ki67 and TGF-ß RII and a TUNEL assay. The presence and levels of 39 bacterial taxa were analyzed using the Checkerboard DNA-DNA hybridization method. The profiles of NO released from the HPMC/GSNO formulations were characterized using chemiluminescence. RESULTS: The HPMC/GSNO formulations were found to provide sustained release of NO for more than 4 h at concentration-dependent rates of 14 to 80 nmol/mL/h. Treatment with HPMC/GSNO (0.5 mM) significantly reduced mucosal damage, inflammatory alterations and cell death associated with 5-FU-induced oral mucositis on day 14 but not on day 10. HPMC/GSNO administration also reversed the inhibitory effect of 5-FU on cell proliferation on day 14. In addition, we observed that the chemotherapy significantly increased the levels and/or prevalence of several bacterial species. CONCLUSION: Topical HPMC/GSNO accelerates mucosal recovery, reduces inflammatory parameters, speeds up re-epithelization and decreases levels of periodontopathic species in mucosal ulcers.

S-nitrosoglutathione inhibits inducible nitric oxide synthase upregulation by redox posttranslational modification in experimental diabetic retinopathy.

PURPOSE: Diabetic retinopathy (DR) is associated with nitrosative stress. The purpose of this study was to evaluate the beneficial effects of S-nitrosoglutathione (GSNO) eye drop treatment on an experimental model of DR. METHODS: Diabetes (DM) was induced in spontaneously hypertensive rats (SHR). Treated animals received GSNO eye drop (900 nM or 10 µM) twice daily in both eyes for 20 days. The mechanisms of GSNO effects were evaluated in human RPE cell line (ARPE-19). RESULTS: In animals with DM, GSNO decreased inducible nitric oxide synthase (iNOS) expression and prevented tyrosine nitration formation, ameliorating glial dysfunction measured with glial fibrillary acidic protein, resulting in improved retinal function. In contrast, in nondiabetic animals, GSNO induced oxidative/nitrosative stress in tissue resulting in impaired retinal function. Nitrosative stress was present markedly in the RPE layer accompanied by c-wave dysfunction. In vitro study showed that treatment with GSNO under high glucose condition counteracted nitrosative stress due to iNOS downregulation by S-glutathionylation, and not by prevention of decreased GSNO and reduced glutathione levels. This posttranslational modification probably was promoted by the release of oxidized glutathione through GSNO denitrosylation via GSNO-R. In contrast, in the normal glucose condition, GSNO treatment promoted nitrosative stress by NO formation. CONCLUSIONS: In this study, a new therapeutic modality (GSNO eye drop) targeting nitrosative stress by redox posttranslational modification of iNOS was efficient against early damage in the retina due to experimental DR. The present work showed the potential clinical implications of balancing the S-nitrosoglutathione/glutathione system in treating DR.

Nitric oxide-releasing poly(vinyl alcohol) film for increasing dermal vasodilation.

Pathological conditions associated with the impairment of nitric oxide (NO) production in the vasculature, such as Raynaud's syndrome and diabetic angiopathy, have stimulated the development of new biomaterials capable of delivering NO topically. With this purpose, we modified poly(vinyl-alcohol) (PVA) by chemically crosslinking it via esterification with mercaptosuccinic acid. This reaction allowed the casting of sulfhydrylated PVA (PVA-SH) films. Differential scanning calorimetry and X-ray diffractometry showed that the crosslinking reaction completely suppressed the crystallization of PVA, leading to a non-porous film with a homogeneous distribution of -SH groups. The remaining free hydroxyl groups in the PVA-SH network conferred partial hydrophylicity to the material, which was responsible for a swelling degree of ca. 110%. The PVA-SH films were subjected to an S-nitrosation reaction of the -SH groups, yielding a PVA containing S-nitrosothiol groups (PVA-SNO). Amperometric and chemiluminescence measurements showed that the PVA-SNO films were capable of releasing NO spontaneously after immersion in physiological medium. Laser Doppler-flowmetry, used to assess the blood flow in the dermal microcirculation, showed that the topical application of hydrated PVA-SNO films on the health skin led to a dose- and time-dependent increase of more than 5-fold in the dermal baseline blood flow in less than 10min, with a prolonged action of more than 4h during continuous application. These results show that PVA-SNO films might emerge as a new material with potential for the topical treatment of microvascular skin disorders.

S-nitroso-N-acetylcysteine attenuates liver fibrosis in experimental nonalcoholic steatohepatitis.

S-Nitroso-N-acetylcysteine (SNAC) is a water soluble primary S-nitrosothiol capable of transferring and releasing nitric oxide and inducing several biochemical activities, including modulation of hepatic stellate cell activation. In this study, we evaluated the antifibrotic activity of SNAC in an animal model of nonalcoholic steatohepatitis (NASH) induced in Sprague-Dawley rats fed with a choline-deficient, high trans fat diet and exposed to diethylnitrosamine for 8 weeks. The rats were divided into three groups: SNAC, which received oral SNAC solution daily; NASH, which received the vehicle; and control, which received standard diet and vehicle. Genes related to fibrosis (matrix metalloproteinases [MMP]-13, -9, and -2), transforming growth factor ß-1 [TGFß-1], collagen-1α, and tissue inhibitors of metalloproteinase [TIMP-1 and -2] and oxidative stress (heat-shock proteins [HSP]-60 and -90) were evaluated. SNAC led to a 34.4% reduction in the collagen occupied area associated with upregulation of MMP-13 and -9 and downregulation of HSP-60, TIMP-2, TGFß-1, and collagen-1α. These results indicate that oral SNAC administration may represent a potential antifibrotic treatment for NASH.

Skin vasodilation and analgesic effect of a topical nitric oxide-releasing hydrogel.

New approaches based on topical treatments are needed for treating pain and impaired dermal blood flow. We used a topical Pluronic F127 hydrogel containing S-nitrosoglutathione (GSNO) as a prodrug to generate free NO, an effector molecule that exerts both dermal vasodilation and antinociceptive effects. GSNO-containing hydrogels underwent gelation above 12 °C and released free NO at rates that were directly dependent on the GSNO concentration in the range of 50-150 mM. The topical application of this material led to dose-response dermal vasodilation in healthy volunteers and to a reduction of up to 50 % of the hypernociception intensity in Wistar rats that were subjected to inflammatory pain. Mechanistic investigations indicated that the antinociceptive effect of the topical F127/GSNO hydrogels is produced by the local activation of the cGMP/PKG/KATP channel-signaling pathway, which was stimulated by the free NO that diffused through the skin. These results expand the scope of the biomedical applications of this material and may represent a new approach for the topical treatment of inflammatory pain.