A prodrug of cysteine, L-2-oxothiazolidine-4-carboxylic acid, regulates vascular permeability by reducing vascular endothelial growth factor expression in asthma

Induction of heme oxygenase-1 antagonizes PM2.5-induced pulmonary VEGFA expression through regulating HIF-1α

Particulate matter (PM) 2.5 has long been regarded as a major risk factor of the respiratory system, which constitutes a threat to human health. Although the positive relationship between PM2.5 exposure and the development of respiratory diseases has been well established, limited studies investigate the intrinsic self-protection mechanisms against PM2.5-induced respiratory injuries. Excessive pulmonary inflammation served as a key pathogenic mechanism in PM2.5-induced airway dysfunction, and we have previously shown that PM2.5 induced the production of vascular endothelial growth factor A (VEGFA) in the bronchial epithelial cells, which subsequently led to pulmonary inflammatory responses. In the current study, we found that PM2.5 also concurrently induced the expression of the stress-responsive protein heme oxygenase-1 (HO-1) along with VEGFA in the bronchial epithelial cells both in vivo and in vitro. Importantly, knocking down of HO-1 expression significantly increased the synthesis and secretion of VEGFA; while overexpression of HO-1 showed the opposite effects, indicating that HO-1 induction can antagonize VEGFA production in the bronchial epithelial cells upon PM2.5 exposure. Mechanistically, HO-1 inhibited PM2.5-evoked VEGFA induction through modulating hypoxia-inducible factor 1 alpha (HIF-1α), which was the upstream transcriptional factor of VEGFA. More specifically, HO-1 could not only inhibit HIF-1α expression, but also suppress its transactivity. Taken together, our results suggested that HO-1 was an intrinsic protective factor against PM2.5-induced pulmonary VEGFA production with a mechanism relating to HIF-1α, thus providing a potential treatment strategy against PM2.5 triggered airway injuries.

Cysteine Donor-Based Brain-Targeting Prodrug: Opportunities and Challenges

Overcoming blood-brain barrier (BBB) to improve brain bioavailability of therapeutic drug remains an ongoing concern. Prodrug is one of the most reliable approaches for delivering agents with low-level BBB permeability into the brain. The well-known antioxidant capacities of cysteine (Cys) and its vital role in glutathione (GSH) synthesis indicate that Cys-based prodrug could potentiate therapeutic drugs against oxidative stress-related neurodegenerative disorders. Moreover, prodrug with Cys moiety could be recognized by the excitatory amino acid transporter 3 (EAAT3) that is highly expressed at the BBB and transports drug into the brain. In this review, we summarized the strategies of crossing BBB, properties of EAAT3 and its natural substrates, Cys and its donors, and Cys donor-based brain-targeting prodrugs by referring to recent investigations. Moreover, the challenges that we are faced with and future research orientations were also addressed and proposed. It is hoped that present review will provide evidence for the pursuit of novel Cys donor-based brain-targeting prodrug.

X-ray crystal structures and anti-breast cancer property of 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acids

The present article encompasses resolution and X-ray crystallographically confirmed absolute stereochemistry-correlated anticancer activity of diastereomeric 3-(tert-butoxycarbonyl)-2-(2-aryl)thiazolidine-4-carboxylic acids against MCF7 breast cancer cells.

Recent developments in the role of reactive oxygen species in allergic asthma

Allergic asthma has a global prevalence, morbidity, and mortality. Many environmental factors, such as pollutants and allergens, are highly relevant to allergic asthma. The most important pathological symptom of allergic asthma is airway inflammation. Accordingly, the unique role of reactive oxygen species (ROS) had been identified as a main reason for this respiratory inflammation. Many studies have shown that inhalation of different allergens can promote ROS generation. Recent studies have demonstrated that several pro-inflammatory mediators are responsible for the development of allergic asthma. Among these mediators, endogenous or exogenous ROS are responsible for the airway inflammation of allergic asthma. Furthermore, several inflammatory cells induce ROS and allergic asthma development. Airway inflammation, airway hyper-responsiveness, tissue injury, and remodeling can be induced by excessive ROS production in animal models. Based on investigations of allergic asthma and ROS formation mechanisms, we have identified several novel anti-inflammatory therapeutic treatments. This review describes the recent data linking ROS to the pathogenesis of allergic asthma.

Transport via SLC5A8 (SMCT1) is obligatory for 2-oxothiazolidine-4-carboxylate to enhance glutathione production in retinal pigment epithelial cells

PURPOSE

To evaluate the role of SLC5A8 in the transport of 2-oxothiazolidine-4-carboxylate (OTC) and to determine whether OTC augments glutathione production in RPE cells, thereby providing protection against oxidative stress.

METHODS

SLC5A8-mediated transport of OTC was monitored in Xenopus laevis oocytes by electrophysiological means. Saturation kinetics, Na(+)-activation kinetics, and inhibition by ibuprofen were analyzed by monitoring OTC-induced currents as a measure of transport activity. Oxidative stress was induced in ARPE-19 cells and primary RPE cells isolated from wild type and Slc5a8(-/-) mouse retinas using H(2)O(2), and the effects of OTC on cell death and intracellular glutathione concentration were examined.

RESULTS

Heterologous expression of human SLC5A8 in X. laevis oocytes induced Na(+)-dependent inward currents in the presence of OTC under voltage-clamp conditions. The transport of OTC via SLC5A8 was saturable, with a K(t) of 104 ± 3 μM. The Na(+)-activation kinetics was sigmoidal with a Hill coefficient of 1.9 ± 0.1, suggesting involvement of two Na(+) in the activation process. Ibuprofen, a blocker of SLC5A8, inhibited SLC5A8-mediated OTC transport; the concentration necessary for half-maximal inhibition was 17 ± 1 μM. OTC increased glutathione levels and protected ARPE-19 and primary RPE cells isolated from wild type mouse retinas from H(2)O(2)-induced cell death. These effects were abolished in primary RPE isolated from Slc5a8(-/-) mouse retinas.

CONCLUSIONS

OTC is a transportable substrate for SLC5A8. OTC augments glutathione production in RPE cells, thereby protecting them from oxidative damage. Transport via SLC5A8 is obligatory for this process.

Angiopoietin-1 treatment reduces inflammation but does not prevent ventilator-induced lung injury

Background

Loss of integrity of the epithelial and endothelial barriers is thought to be a prominent feature of ventilator-induced lung injury (VILI). Based on its function in vascular integrity, we hypothesize that the angiopoietin (Ang)-Tie2 system plays a role in the development of VILI. The present study was designed to examine the effects of mechanical ventilation on the Ang-Tie2 system in lung tissue. Moreover, we evaluated whether treatment with Ang-1, a Tie2 receptor agonist, protects against inflammation, vascular leakage and impaired gas exchange induced by mechanical ventilation.

Methods

Mice were anesthetized, tracheotomized and mechanically ventilated for 5 hours with either an inspiratory pressure of 10 cmH₂O (‘low’ tidal volume ∼7.5 ml/kg; LV_T) or 18 cmH₂O (‘high’ tidal volume ∼15 ml/kg; HV_T). At initiation of HV_T-ventilation, recombinant human Ang-1 was intravenously administered (1 or 4 µg per animal). Non-ventilated mice served as controls.

Results

HV_T-ventilation influenced the Ang-Tie2 system in lungs of healthy mice since Ang-1, Ang-2 and Tie2 mRNA were decreased. Treatment with Ang-1 increased Akt-phosphorylation indicating Tie2 signaling. Ang-1 treatment reduced infiltration of granulocytes and expression of keratinocyte-derived chemokine (KC), macrophage inflammatory protein (MIP)-2, monocyte chemotactic protein (MCP)-1 and interleukin (IL)-1β caused by HV_T-ventilation. Importantly, Ang-1 treatment did not prevent vascular leakage and impaired gas exchange in HV_T-ventilated mice despite inhibition of inflammation, vascular endothelial growth factor (VEGF) and Ang-2 expression.

Conclusions

Ang-1 treatment downregulates pulmonary inflammation, VEGF and Ang-2 expression but does not protect against vascular leakage and impaired gas exchange induced by HV_T-ventilation.

The roles of phytochemicals in bronchial asthma

Despite gaps in our knowledge of how phytochemicals interfere with cellular functions, several natural plant products are utilized to prevent or treat a wide range of diseases. Identification of an agent with therapeutic potential requires multiple steps involving in vitro studies, efficacy and toxicity studies in animal models, and then human clinical trials. This review provides a brief introduction on natural products that may help to treat and/or prevent bronchial asthma and describes our current understanding of their molecular mechanisms based on various in vitro, in vivo, and clinical studies. We focus on the anti-inflammatory and anti-vascular actions of the plant products and other roles beyond the anti-oxidative effects.

Angiogenesis and lymphangiogenesis in bronchial asthma

Neovascularization plays a prominent role in inflammation and tissue remodeling in several chronic inflammatory disorders. Vessel number and size, vascular surface area and vascular leakage are all increased in biopsies from patients with asthma. High levels of VEGF and other angiogenic factors have been detected in tissues and biological samples of patients with asthma and correlate with disease activity and inversely with airway hyper-responsiveness. Inflammation in the lung stimulates the growth of new blood vessels and these contribute to the airway obstruction or airway hyper-responsiveness, or both. Effector cells of inflammation (human lung mast cells, basophils, eosinophils, macrophages, etc.) are major sources of a vast array of angiogenic and lymphangiogenic factors. Inhaled corticosteroids reduce vascularity and growth factor expression and might modulate bronchial vascular remodeling in asthma. Specific antagonists to VEGF and other angiogenic factors and their receptors might help to control chronic airway inflammation and vascular remodeling and offer a novel approach for the treatment of chronic inflammatory lung disorders.

A novel dithiol amide CB3 attenuates allergic airway disease through negative regulation of p38 mitogen-activated protein kinase

RATIONALE

Cellular redox homeostasis altered by excessive production of reactive oxygen species (ROS) and weakening of the antioxidant defense leads to oxidative stress. Oxidative stress is characterized as a decrease in glutathione/glutathione disulfide (GSH/GSSG) and the triggering of a number of the redox-sensitive signaling cascades. Recent studies have demonstrated that ROS play an important role in the pathogenesis of airway inflammation and hyperresponsiveness.

OBJECTIVES

Here we characterized for the first time the protective properties of a new hydrophobic thiol compound, N-acetyl cysteine proline cysteine amide (CB3), in allergic airway diseases.

METHODS

We used ovalbumin (OVA)-inhaled mice to evaluate the role of CB3 as an antiinflammatory reagent and to determine its molecular signaling activity in allergic airways.

MEASUREMENTS AND MAIN RESULTS

The administration of CB3 (1-50 mg/kg) to OVA-inhaled mice restored the decreased GSH levels, enhanced IL-10 expression, and significantly reduced the increase of Th2 cytokines and OVA-specific IgE. CB3 decreased the number of inflammatory cells and airway hyperresponsiveness in the lungs. We also found that the administration of CB3 dramatically decreased the nuclear translocation of the nuclear factor-κB (NF-κB) and the phosphorylation of p38 mitogen-activated protein kinases (MAPKs) in lungs after OVA inhalation. In addition, allergen-induced airway inflammation and hyperresponsiveness were substantially reduced by the administration of inhibitors of NF-κB and p38 MAPK, BAY 11-7085, and SB 239063, respectively.

CONCLUSIONS

These results suggest that CB3 attenuates allergic airway disease by up-regulation of GSH levels as well as inhibition of NF-κB and p38 MAPK activity.

Pulmonary exposure to diesel exhaust particles promotes cerebral microvessel thrombosis: protective effect of a cysteine prodrug l-2-oxothiazolidine-4-carboxylic acid

Inhaled particulate matter is associated with increased cerebro- and cardiovascular events. However, the systemic mechanisms underlying these effects remain unclear. In the present study, we investigated the mechanisms underlying the relationship between airway and systemic inflammation and pial cerebral venular thrombosis, 24h after intratracheal (i.t.) instillation of diesel exhaust particles (DEP; 15 or 30 microg/mouse) or saline (control). Doses of 15 and 30 microg/mouse induced a dose-dependent macrophage and neutrophil influx into the bronchoalveolar lavage (BAL) fluid with elevation of total proteins and Trolox equivalent antioxidant capacity (TEAC), but without IL-6 release. Similarly, in plasma, IL-6 concentrations did not increase but the TEAC was significantly and dose-dependently decreased. The number of platelets and the tail bleeding time were both significantly reduced after exposure to DEP (30 microg). Interestingly, the same dose showed platelet proaggregatory effect in mouse pial cerebral venules. Pretreatment with the cysteine prodrug l-2-oxothiazolidine-4-carboxylic acid (OTC, 80 mg/kg) 24 and 1h before i.t. DEP (30 microg), abolished the DEP-induced macrophage and neutrophil influx, and the increase of TEAC in BAL. Lung histopathology confirmed the protective effect of OTC on DEP-induced lung inflammation. OTC also reversed the decrease of TEAC concentrations in plasma, the shortening of the bleeding time, and the thrombotic effect of DEP in pial cerebral venules. We conclude that pulmonary exposure to DEP cause oxidative stress responsible, at least partially, for the pulmonary and systemic inflammation and thrombotic events in the pial cerebral microvessels of mice. OTC pretreatment abrogated these effects through its ability to balance oxidant-antioxidant status.

Inhibitory effect of Platycodi Radix on ovalbumin-induced airway inflammation in a murine model of asthma

Asthma is a chronic inflammatory disease of the airways characterized by an associated increase in airway responsiveness. In this study, we investigated the inhibitory effect of an aqueous extract from the root of Platycodi Radix (Changkil: CK) on airway inflammation in a murine model of asthma. Mice were sensitized and challenged by ovalbumin (OVA) inhalation to induce chronic airway inflammation and airway remodeling. CK markedly decreased the number of infiltrated inflammatory cells and the levels of Th1 and Th2 cytokines and chemokines compared with those in the OVA-induced group. In addition, CK reduced OVA-specific IgE levels in bronchoalveolar lavage (BAL) fluid. Based on lung histopathological studies, inflammatory cell infiltration and mucus hypersecretion were inhibited by CK administration compared to that in the OVA-induced group. Lung weight was reduced after CK administration. Also, increased generation of ROS in BAL fluid, as well as NF-kappaB nuclear translocation, by inhalation of OVA was diminished by CK. Moreover, CK reduced the OVA-induced upregulation of matrix metalloproteases activity. These findings indicate that oxidative stress may play a crucial role in the pathogenesis of bronchial asthma induced by OVA and that CK may be useful as an adjuvant therapy for the treatment of bronchial asthma.

Angiopoietin-1 variant, COMP-Ang1 attenuates hydrogen peroxide-induced acute lung injury

Reactive oxygen species (ROS) play a crucial role in acute lung injury. Tissue inflammation, the increased vascular permeability, and plasma exudation are cardinal features of acute lung injury. Angiopoietin-1 (Ang1) has potential therapeutic applications in preventing vascular leakage and also has beneficial effects in several inflammatory disorders. Recently developed COMP-Ang1 is more potent than native Ang1 in phosphorylating tyrosine kinase with immunoglobulin and EGF homology domain 2 receptor in endothelial cells. However, there are no data on effects and related molecular mechanisms of COMP- Ang1 on ROS-induced acute lung injury. We used hydrogen peroxide (H2O2)-inhaled mice to evaluate the effect of COMP-Ang1 on pulmonary inflammation, bronchial hyper-responsiveness, and vascular leakage in acute lung injury. The results have revealed that VEGF expression, the levels of IL-4, TNF-alpha, IL-1beta, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in lungs, the levels of hypoxia-inducible factor-1alpha (HIF-1alpha) and NF-kappaB in nuclear protein extracts, phosphorylation of Akt, and vascular permeability were increased after inhalation of H2O2 and that the administration of COMP-Ang1 markedly reduced airway hyper-responsiveness, pulmonary inflammation, plasma extravasation, and the increases of cytokines, adhesion molecules, and VEGF in lungs treated with H2O2. We have also found that the activation of HIF-1a and NF-kB and the increase of phosphoinositide 3-kinase activity in lung tissues after H2O2 inhalation were decreased by the administration of COMP-Ang1. These results suggest that COMP-Ang1 ameliorates ROS-induced acute lung injury through attenuating vascular leakage and modulating inflammatory mediators.

Differential role of peroxiredoxin II (PrxII) on the expression of toll-like receptor 4 (TLR4) and B-cell activating factor (BAFF) in ovalbumin (OVA)-induced mouse asthma

Peroxiredoxin II (PrxII) is one of reactive oxygen species (ROS)-degrading enzyme. Here, we investigated the role of PrxII on toll-like receptor 4 (TLR4) and B-cell activating factor (BAFF) expression in ovalbumin (OVA)-induced mouse asthma. We used ROS-producing PrxII-/- mice of which cells up-regulate BAFF expression. As significant changes were detected in TLR4 mRNA with real-time quantitative RT-PCR analysis, TLR4 protein was decreased in PrxII-/- mouse splenocytes and peritoneal macrophages, compared to wild type cells. Airway hyper-responsiveness (AHR) was more severe in PrxII-/- mice than wild type mice, which was measured by the level of various parameters, number of eosinophils, IgE level, airway thickness, and mucous secretion. BAFF was detected in cells surrounding airways of OVA-induced mouse and it was highly augmented in PrxII-/- mice. BAFF promoter activity was also higher in PrxII-/- mouse embryonic fibroblast (MEF) than in wild type MEF. Collectively, results show that PrxII may have benefits in asthma through reducing ROS. It suggests that BAFF and TLR4 expressions are differentially regulated by PrxII and TLR4 protein level may not be crucial in OVA-induced asthma.

Neovastat (AE-941) inhibits the airway inflammation via VEGF and HIF-2 alpha suppression

Vascular endothelial growth factor (VEGF) contributes to airway inflammation and angiogenesis in asthma. Hypoxia inducible factor (HIF), the most potent regulator of VEGF, is a heterodimer of a constitutively expressed beta subunit and an oxygen-regulated alpha subunit (HIF-alpha). Three HIF-alpha isoforms have been described, of which HIF-2 alpha are abundantly expressed in lung tissue. Neovastat is a naturally occurring inhibitor of angiogenesis derived from marine cartilage. We previously reported that Neovastat can inhibit the airway inflammation in asthma. In this study, we hypothesized that the anti-inflammatory effect of Neovastat is mediated with inhibition of VEGF and HIF-2 alpha. BALB/c mice were immunized subcutaneously and challenged with inhaled ovalbumin (OVA). Neovastat was administrated by gavage three times with 12-h interval, beginning at 30 min before OVA inhalation. VEGF concentration in bronchoalveolar lavage fluid was measured by ELISA. We evaluate the expression of VEGF and HIF-2 alpha in lung tissue by immunohistochemistry. Mice treated with Neovastat had significantly reduced inflammatory cell count in BAL fluid compared with untreated asthmatic mice. Furthermore, Mice treated with Neovastat showed significantly reduced VEGF and HIF-2 alpha expression on lung tissue. These results suggest that anti-inflammatory effects of Neovastat could be linked to inhibition of VEGF and HIF-2 alpha.

Antioxidant down-regulates interleukin-18 expression in asthma

An alteration in the balance between a T-helper type 2 cell (Th2) response and a Th1 response may predispose to the development of bronchial asthma. Interleukin-18 (IL-18) has an ability to promote both Th1 and Th2 responses, depending on the surrounding cytokine environment. Reactive oxygen species (ROS) play a crucial role in the pathogenesis of airway inflammation and hyperresponsiveness. Recent studies have demonstrated that antioxidants are able to reduce airway inflammation and hyperreactivity in animal models of asthma. In this study, we used a C57BL/6 mouse model of allergic asthma to examine the effects of antioxidants on the regulation of IL-18 expression. Our present study with ovalbumin-induced murine model of asthma revealed that ROS production in cells from bronchoalveolar lavage fluids was increased and that administration of L-2-oxothiazolidine-4-carboxylic acid or alpha-lipoic acid reduced the increased levels of ROS, the increased expression of IL-18 protein and mRNA, airway inflammation, and bronchial hyperresponsiveness. Our results also showed that antioxidants down-regulated a transcription factor, nuclear factor-kappaB (NF-kappaB), activity. These results indicate that antioxidants may reduce IL-18 expression in asthma by inhibiting the activity of NF-kappaB and suggest that ROS regulate the IL-18 expression.

Sparing of methionine requirements: evaluation of human data takes sulfur amino acids beyond protein

The intimate relation between amino acids and protein and nitrogen requirements is well recognized. Nutrition research has focused on the capacity of food to meet the need for nitrogen and indispensable amino acids (IAA) and led to the conclusion that the quality, not just the quantity, of protein is critical. This is especially relevant in regard to the sulfur amino acids (SAA) methionine and cysteine because of the increased understanding of their relation to chronic diseases (e.g., cardiovascular disease, dementia, cirrhosis), immunomodulation, DNA transcription, and RNA translation. Considerable effort has been expended to determine whether and to what extent cysteine can spare the requirement for the IAA methionine. In vivo studies in humans generally concur that the dietary requirement of the SAA ranges between 13 and 16 mg.kg(-1).d(-1), but how much can be met by cysteine relative to methionine remains controversial. This review examines the current status of in vivo estimates of methionine and cysteine requirements in human adults and considers needs beyond what is necessary for protein synthesis. Factors influencing the utilization of methionine and cysteine, especially those conditions that lead to toxicity on the one hand or beneficial effects on the other, are discussed. Data on alternative dietary sources of methyl groups (e.g., betaine, choline, phosphatidylcholine, S-adenosylmethionine, S-methylmethionine) or sulfur (e.g., N-acetylcysteine or L-2-oxothiazolidine-4-carboxylic acid) support a role for the SAA "beyond protein." Other pathways may influence the specific requirement for methionine and/or cysteine, especially when the person is challenged by disease, inadequate availability of food, or environmental stress.

Hydrogen peroxide induces vascular permeability via regulation of vascular endothelial growth factor

Oxidative stress plays critical roles in initiation and/or worsening of respiratory disease process. Although reactive oxygen species (ROS) are shown to cause vascular leakage, the mechanisms by which ROS induce an increase in vascular permeability are not clearly understood. In this study, we have used a murine model to evaluate the effect of hydrogen peroxide (H(2)O(2)) to examine roles of ROS and the molecular mechanism in vascular permeability. The results have revealed that ROS levels, vascular endothelial growth factor (VEGF) expression, hypoxia-inducible factor-1alpha protein level, airway hyperresponsiveness, and vascular permeability are increased after inhalation of H(2)O(2). Administration of antioxidants markedly reduced plasma extravasation and VEGF levels in lungs treated with H(2)O(2). These results indicate that ROS may modulate vascular permeability via upregulation of VEGF expression.