Molecular mechanism for activation and regulation of matrix metalloproteinases during bacterial infections and respiratory inflammation

The Balance between Protealysin and Its Substrate, the Outer Membrane Protein OmpX, Regulates Serratia proteamaculans Invasion

Serratia are opportunistic bacteria, causing infections in plants, insects, animals and humans under certain conditions. The development of bacterial infection in the human body involves several stages of host-pathogen interaction, including entry into non-phagocytic cells to evade host immune cells. The facultative pathogen Serratia proteamaculans is capable of penetrating eukaryotic cells. These bacteria synthesize an actin-specific metalloprotease named protealysin. After transformation with a plasmid carrying the protealysin gene, noninvasive E. coli penetrate eukaryotic cells. This suggests that protealysin may play a key role in S. proteamaculans invasion. This review addresses the mechanisms underlying protealysin's involvement in bacterial invasion, highlighting the main findings as follows. Protealysin can be delivered into the eukaryotic cell by the type VI secretion system and/or by bacterial outer membrane vesicles. By cleaving actin in the host cell, protealysin can mediate the reversible actin rearrangements required for bacterial invasion. However, inactivation of the protealysin gene leads to an increase, rather than decrease, in the intensity of S. proteamaculans invasion. This indicates the presence of virulence factors among bacterial protealysin substrates. Indeed, protealysin cleaves the virulence factors, including the bacterial surface protein OmpX. OmpX increases the expression of the EGFR and β1 integrin, which are involved in S. proteamaculans invasion. It has been shown that an increase in the invasion of genetically modified S. proteamaculans may be the result of the accumulation of full-length OmpX on the bacterial surface, which is not cleaved by protealysin. Thus, the intensity of the S. proteamaculans invasion is determined by the balance between the active protealysin and its substrate OmpX.

Curcumin Oxidation Is Required for Inhibition of Helicobacter pylori Growth, Translocation and Phosphorylation of Cag A

Curcumin is a potential natural remedy for preventing Helicobacter pylori-associated gastric inflammation and cancer. Here, we analyzed the effect of a phospholipid formulation of curcumin on H. pylori growth, translocation and phosphorylation of the virulence factor CagA and host protein kinase Src in vitro and in an in vivo mouse model of H. pylori infection. Growth of H. pylori was inhibited dose-dependently by curcumin in vitro. H. pylori was unable to metabolically reduce curcumin, whereas two enterobacteria, E. coli and Citrobacter rodentium, which efficiently reduced curcumin to the tetra- and hexahydro metabolites, evaded growth inhibition. Oxidative metabolism of curcumin was required for the growth inhibition of H. pylori and the translocation and phosphorylation of CagA and cSrc, since acetal- and diacetal-curcumin that do not undergo oxidative transformation were ineffective. Curcumin attenuated mRNA expression of the H. pylori virulence genes cagE and cagF in a dose-dependent manner and inhibited translocation and phosphorylation of CagA in gastric epithelial cells. H. pylori strains isolated from dietary curcumin-treated mice showed attenuated ability to induce cSrc phosphorylation and the mRNA expression of the gene encoding for IL-8, suggesting long-lasting effects of curcumin on the virulence of H. pylori. Our work provides mechanistic evidence that encourages testing of curcumin as a dietary approach to inhibit the virulence of CagA.

The impact of Sambucus nigra L. extract on inflammation, oxidative stress and tissue remodeling in a rat model of lipopolysaccharide-induced subacute rhinosinusitis

Rhinosinusitis is a common disorder related to inflammation of paranasal sinuses and nasal cavity mucosa. Herbal medicines could be an option in the treatment of rhinosinusitis due to their anti-inflammatory and anti-oxidative properties. The study aims to investigate the effect of intranasal Sambucus nigra L. subsp. nigra (SN) extract against inflammation, oxidative stress, and tissue remodeling in nasal and sinus mucosa, but also in serum, lungs, and brain, in Wistar rat model of subacute sinonasal inflammation induced by local administration of lipopolysaccharides (LPS), from Escherichia Coli. The cytokines (TNF-α, IL-1β, IL-6) and oxidative stress (malondialdehyde) in nasal mucosa, blood, lungs, and brain were analyzed. In addition, a histopathological examination was performed, and NF-kB, MMP2, MMP9, TIMP1 expressions were also evaluated in nasal mucosa. Both doses of LPS increased the production of cytokines in all the investigated tissues, especially in the nasal mucosa and blood (p < 0.01 and p < 0.05), and stimulated their secretion in the lungs, and partially in the brain. Malondialdehyde increased in all the investigated tissues (p < 0.01 and p < 0.05). In parallel, upregulation of NF-kB and MMP2 expressions with downregulation of TIMP1, particularly at high dose of LPS, was observed. SN extract reduced the local inflammatory response, maintained low levels of IL-6, TNF-α, and IL-1β. In lungs, SN reduced all cytokines levels while in the brain, the protective effect was noticed only on IL-6. Additionally, SN diminished lipid peroxidation and downregulated NF-kB in animals exposed to a low dose of LPS, with increased TIMP1 expression, while in animals treated with a high dose of LPS, SN increased NF-kB, MMP2, and MMP9 levels. In conclusion, SN extract diminished the inflammatory response, reduced generation of reactive oxygen species (ROS) and, influenced MMPs expressions, suggesting the benficial effect of SN extract on tissue remodeling in subacute rhinosinusitis and on systemic inflammatory response.

Oxidative and Nitrosative Stress in the Pathogenesis of Obstructive Lung Diseases of Increasing Severity

The imbalance between increased oxidative agents and antioxidant defence mechanisms is central in the pathogenesis of obstructive lung diseases such as asthma and COPD. In these patients, there are increased levels of reactive oxygen species. Superoxide anions (O₂ -), Hydrogen Peroxide (H₂O₂) and hydroxyl radicals (•OH) are critical for the formation of further cytotoxic radicals in the bronchi and lung parenchyma. Chronic inflammation, partly induced by oxidative stress, can further increase the oxidant burden through activated phagocytic cells (neutrophils, eosinophils, macrophages), particularly in severer disease states. Antioxidants and anti-inflammatory genes are, in fact, frequently downregulated in diseased patients. Nrf2, which activates the Antioxidant Response Element (ARE) leading to upregulation of GPx, thiol metabolism-associated detoxifying enzymes (GSTs) and stressresponse genes (HO-1) are all downregulated in animal models and patients with asthma and COPD. An exaggerated production of Nitric Oxide (NO) in the presence of oxidative stress can promote the formation of oxidizing reactive nitrogen species, such as peroxynitrite (ONO₂ -), leading to nitration and DNA damage, inhibition of mitochondrial respiration, protein dysfunction, and cell damage in the biological systems. Protein nitration also occurs by activation of myeloperoxidase and H₂O₂, promoting oxidation of nitrite (NO₂ -). There is increased nitrotyrosine and myeloperoxidase in the bronchi of COPD patients, particularly in severe disease. The decreased peroxynitrite inhibitory activity found in induced sputum of COPD patients correlates with pulmonary function. Markers of protein nitration - 3- nitrotyrosine, 3-bromotyrosine, and 3-chlorotyrosine - are increased in the bronchoalveolar lavage of severe asthmatics. Targeting the oxidative, nitrosative stress and associated lung inflammation through the use of either denitration mechanisms or new drug delivery strategies for antioxidant administration could improve the treatment of these chronic disabling obstructive lung diseases.

Hydrogen sulfide attenuates hyperhomocysteinemia-induced blood-brain barrier permeability by inhibiting MMP-9

Backgroud: Hyperhomocysteinemia (HHcy) is implicated in various neurovascular disorders including vascular dementia, subarachnoid hemorrhage and stroke. Elevated homocysteine (Hcy) levels are associated with increased oxidative stress and compromised blood-brain barrier (BBB) integrity. Hydrogen sulfide (H₂S) has recently emerged as potent neuroprotective molecule in various neurological conditions including those associated with HHcy. The present study evaluates the protective effect of sodium hydrogen sulfide (NaHS; a source of H₂S) on HHcy-induced BBB dysfunction and underpin molecular mechanisms.Materials and methods: Supplementation of NaHS restored the increased BBB permeability in the cortex and hippocampus of HHcy animals assessed in terms of diffused sodium fluorescein and Evans blue tracer dyes in the brain. Activity of matrix metalloproteinases (MMPs) assessed by gelatinase activity and in situ gelatinase assay was restored to the normal in the cortex and hippocampus of HHcy animals supplemented with NaHS.Results: Application of gelatin zymography revealed that specifically MMP-9 activity was increased in the cortex and hippocampus of HHcy animals, which was inhibited by NaHS supplementation. Real-time RT-PCR analysis showed that NaHS administration also decreased mRNA expression of MMP-9 in the hippocampus of HHcy animals. NaHS supplementation was further observed to reduce water retention in the brain regions of Hcy treated animals.Conclusion: Taken together, these findings suggest that NaHS supplementation ameliorates HHcy-induced BBB permeability and brain edema by inhibiting the mRNA expression and activity of MMP-9. Therefore, H₂S and H₂S releasing drugs may be used as a novel therapeutic approach to treat HHcy-associated neurovascular disorders.

Characteristics of matrix metalloproteinases and their role in embryogenesis of the mammalian respiratory system

The human respiratory system appears as an outgrowth from the ventral wall of the primary foregut and its development includes a series of subsequent processes, dependent on the interactions between endothelial cells, respiratory epithelium and extracellular matrix (ECM). These interactions determine the acquisition of normal structural and functional features of the newly created tissues. The essential role in the morphogenesis of the respiratory system is performed by matrix metalloproteinases (MMPs). MMPs are endopeptidases containing zinc ion in their active center, necessary for the processes of hydrolysis of peptide bonds of substrates. The production of MMPs takes place in most connective tissue cells, leukocytes, macrophages, vascular endothelial cells as well as in neurons, glial cells and in tumor cells. Like other proteolytic enzymes, MMPs are produced and secreted in the form of inactive pro-enzymes, and their activation occurs in the extracellular space. MMPs perform both physiological and pathological functions during tissue modeling and their role in embryogenesis is based on the regulation of angiogenesis processes, stroma formation and cells migration. This article aims to characterize, discuss and demonstrate the activity and the role of MMPs in the subsequent stages of respiratory development.

The combined effect of pomegranate extract and tangeretin on the DMBA-induced breast cancer model

The aim of this study was to investigate the protective effects of pomegranate extract and tangeretin alone or in combination in DMBA-induced rat breast cancer model. A total of 68 female rats were randomly divided into 8 groups. The first 4 groups were designed as controls for cancer and treatment groups, and the control groups were composed of only control (C), Pomegranate (P), Tangeretin (T), and Pomegranate+Tangeretin (P+T) groups. The other four groups were designed as cancer and treatment groups and were composed of DMBA (D) and DMBA+Pomegranate (D+P), DMBA+Tangeretin (D+T), DMBA+Pomegranate+Tangeretin (D+P+T) groups. Tumor markers and angiogenesis parameters were studied from plasma samples obtained from rats. Histopathological, immunohistochemical, and TUNEL analyses and expressions of proteins affecting apoptosis and cell cycle were determined in breast tissue samples. In the DMBA group, plasma CA15-3, CEA, VEGF, MMP-9, and NF-κB levels were significantly increased compared to the controls, but significant decreases were observed in these parameters except MMP-9 in the treatment groups. It was observed that p53 and Bax expressions significantly increased in both D+P and D+P+T groups compared to the DMBA group, and these findings were supported by Tunel and immunohistochemical findings. Cyclin D1 expressions were found to be significantly decreased only in the D+T group and supported by TUNEL and immunohistochemical findings. Immunohistochemical ER-α and Ki-67 immune reactivities were significantly decreased in all treatment groups compared to the DMBA group. Our results showed that combined application of pomegranate extract and tangeretin may be more beneficial in preventing breast cancer development.

Diabetic Retinopathy: Mitochondria Caught in a Muddle of Homocysteine

Diabetic retinopathy is one of the most feared complications of diabetes. In addition to the severity of hyperglycemia, systemic factors also play an important role in its development. Another risk factor in the development of diabetic retinopathy is elevated levels of homocysteine, a non-protein amino acid, and hyperglycemia and homocysteine are shown to produce synergistic detrimental effects on the vasculature. Hyperhomocysteinemia is associated with increased oxidative stress, and in the pathogenesis of diabetic retinopathy, oxidative stress-mitochondrial dysfunction precedes the development of histopathology characteristic of diabetic retinopathy. Furthermore, homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), and SAM is a co-substrate of DNA methylation. In diabetes, DNA methylation machinery is activated, and mitochondrial DNA (mtDNA) and several genes associated with mitochondrial homeostasis undergo epigenetic modifications. Consequently, high homocysteine, by further affecting methylation of mtDNA and that of genes associated with mtDNA damage and biogenesis, does not give any break to the already damaged mitochondria, and the vicious cycle of free radicals continues. Thus, supplementation of sensible glycemic control with therapies targeting hyperhomocysteinemia could be valuable for diabetic patients to prevent/slow down the development of this sight-threatening disease.

Homocysteine Disrupts Balance between MMP-9 and Its Tissue Inhibitor in Diabetic Retinopathy: The Role of DNA Methylation

High homocysteine is routinely observed in diabetic patients, and this non-protein amino acid is considered as an independent risk factor for diabetic retinopathy. Homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), which is a major methyl donor critical in DNA methylation. Hyperhomocysteinemia is implicated in increased oxidative stress and activation of MMP-9, and in diabetic retinopathy, the activation of MMP-9 facilitates capillary cell apoptosis. Our aim was to investigate the mechanism by which homocysteine activates MMP-9 in diabetic retinopathy. Human retinal endothelial cells, incubated with/without 100 μM homocysteine, were analyzed for MMP-9 and its tissue inhibitor Timp1 expressions and interactions, and ROS levels. Timp1 and MMP-9 promoters were analyzed for methylated and hydroxymethylated cytosine levels (5mC and 5hmC respectively) by the DNA capture method, and DNA- methylating (Dnmt1) and hydroxymethylating enzymes (Tet2) binding by chromatin immunoprecipitation. The results were confirmed in retinal microvessels from diabetic rats receiving homocysteine. Homocysteine supplementation exacerbated hyperglycaemia-induced MMP-9 and ROS levels and decreased Timp1 and its interactions with MMP-9. Homocysteine also aggravated Dnmts and Tets activation, increased 5mC at Timp1 promoter and 5hmC at MMP-9 promoter, and suppressed Timp1 transcription and activated MMP-9 transcription. Similar results were obtained from retinal microvessels from diabetic rats receiving homocysteine. Thus, hyperhomocysteinemia in diabetes activates MMP-9 functionally by reducing Timp1-MMP-9 interactions and transcriptionally by altering DNA methylation-hydroxymethylation of its promoter. The regulation of homocysteine could prevent/slow down the development of retinopathy and prevent their vision loss in diabetic patients.

Natural Inhibitors of Snake Venom Metalloproteinases

Snakebites are a hazard in the tropical world. Although antivenom therapy is effective, it is beset with inherent drawbacks. A better understanding of the major components of snake venoms and their neutralisation will help in improving snakebite treatment. Snake venom metalloproteinases (SVMPs) are responsible for severe haemorrhage, the inhibition of coagulation and platelet aggregation, observed in the victims of snakebite envenoming. Inhibitors from various sources including medicinal plants, animal venoms, and sera are sought to block the pharmacological functions of SVMPs. In this review, we describe the interaction of natural inhibitors with SVMPs. To understand their inhibitory mechanisms, we focussed on the complex structures of these inhibitors and SVMPs. There are three distinct classes of inhibitors; namely, chelators, competitive inhibitors, and non-competitive inhibitors. A small number of inhibitors show their anti-hemorrhagic activity in invivo animal models in treatment mode, but most studies evaluate either invitro neutralisation of enzymatic activity or invivo effects in pre-incubation protocols. We propose the distinct strategies and limitations to design either broad-spectrum or highly selective SVMP inhibitors. The goal of designing broad-spectrum inhibitors against SVMPs capable of effective treatment of snakebites without toxicity has been elusive, probably because of the narrow molecular footprint of inhibitors against a large number of SVMPs with distinct molecular surfaces. Our ability to design highly selective inhibitors is limited by the lack of information of interactions between selective inhibitors and SVMPs. Comparisons of structures of hemorrhagic and non-hemorrhagic SVMPs revealed different distributions of electric charge on the surface of SVMPs, which may be exploited to design specific inhibitors. The specific inhibitors may also be useful to identify target molecules of the SVMPs and help to understand their mechanism of action.

Cystatins 9 and C as a Novel Immunotherapy Treatment That Protects against Multidrug-Resistant New Delhi Metallo-Beta-Lactamase-1-Producing Klebsiella pneumoniae

Multidrug-resistant (MDR) bacterial pneumonia can induce dysregulated pulmonary and systemic inflammation leading to morbidity and mortality. Antibiotics to treat MDR pathogens do not function to modulate the extent and intensity of inflammation and can have serious side effects. Here we evaluate the efficacy of two human cysteine proteinase inhibitors, cystatin 9 (CST9) and cystatin C (CSTC), as a novel immunotherapeutic treatment to combat MDR New Delhi metallo-beta-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae. Our results showed that mice infected intranasally (i.n.) with a 90% lethal dose (LD₉₀) challenge of NDM-1 K. pneumoniae and then treated with the combination of human recombinant CST9 (rCST9) and rCSTC (rCSTs; 50 pg of each i.n. at 1 h postinfection [p.i.] and/or 500 pg of each intraperitoneally [i.p.] at 3 days p.i.) had significantly improved survival compared to that of infected mice alone or infected mice treated with individual rCSTs (P < 0.05). Results showed that both of our optimal rCST treatment regimens modulated pulmonary and systemic proinflammatory cytokine secretion in the serum, lungs, liver, and spleen in infected mice (P < 0.05). Treatment also significantly decreased the bacterial burden (P < 0.05) while preserving lung integrity, with reduced inflammatory cell accumulation compared to that in infected mice. Further, rCST treatment regimens reduced lipid peroxidation and cell apoptosis in the lungs of infected mice. Additionally, in vitro studies showed that rCSTs (50 or 500 pg of each) directly decreased the viability of NDM-1 K. pneumoniae. In conclusion, the data showed that rCST9/rCSTC worked synergistically to modulate host inflammation against MDR NDM-1 K. pneumoniae pneumonia, which significantly improved survival. Therefore, rCST9/rCSTC is a promising therapeutic candidate for the treatment of bacterial pneumonia.

Pyruvate enhancement of cardiac performance: Cellular mechanisms and clinical application

Cardiac contractile function is adenosine-5'-triphosphate (ATP)-intensive, and the myocardium's high demand for oxygen and energy substrates leaves it acutely vulnerable to interruptions in its blood supply. The myriad cardioprotective properties of the natural intermediary metabolite pyruvate make it a potentially powerful intervention against the complex injury cascade ignited by myocardial ischemia-reperfusion. A readily oxidized metabolic substrate, pyruvate augments myocardial free energy of ATP hydrolysis to a greater extent than the physiological fuels glucose, lactate and fatty acids, particularly when it is provided at supra-physiological plasma concentrations. Pyruvate also exerts antioxidant effects by detoxifying reactive oxygen and nitrogen intermediates, and by increasing nicotinamide adenine dinucleotide phosphate reduced form (NADPH) production to maintain glutathione redox state. These enhancements of free energy and antioxidant defenses combine to augment sarcoplasmic reticular Ca²⁺ release and re-uptake central to cardiac mechanical performance and to restore β-adrenergic signaling of ischemically stunned myocardium. By minimizing Ca²⁺ mismanagement and oxidative stress, pyruvate suppresses inflammation in post-ischemic myocardium. Thus, pyruvate administration stabilized cardiac performance, augmented free energy of ATP hydrolysis and glutathione redox systems, and/or quelled inflammation in a porcine model of cardiopulmonary bypass, a canine model of cardiac arrest-resuscitation, and a caprine model of hypovolemia and hindlimb ischemia-reperfusion. Pyruvate's myriad benefits in preclinical models provide the mechanistic framework for its clinical application as metabolic support for myocardium at risk. Phase one trials have demonstrated pyruvate's safety and efficacy for intravenous resuscitation for septic shock, intracoronary infusion for heart failure and as a component of cardioplegia for cardiopulmonary bypass. The favorable outcomes of these trials, which argue for expanded, phase three investigations of pyruvate therapy, mirror findings in isolated, perfused hearts, underscoring the pivotal role of preclinical research in identifying clinical interventions for cardiovascular diseases. Impact statement This article reviews pyruvate's cardioprotective properties as an energy-yielding metabolic fuel, antioxidant and anti-inflammatory agent in mammalian myocardium. Preclinical research has shown these properties make pyruvate a powerful intervention to curb the complex injury cascade ignited by ischemia and reperfusion. In ischemically stunned isolated hearts and in large mammal models of cardiopulmonary bypass, cardiac arrest-resuscitation and hypovolemia, intracoronary pyruvate supports recovery of myocardial contractile function, intracellular Ca²⁺ homeostasis and free energy of ATP hydrolysis, and its antioxidant actions restore β-adrenergic signaling and suppress inflammation. The first clinical trials of pyruvate for cardiopulmonary bypass, fluid resuscitation and intracoronary intervention for congestive heart failure have been reported. Receiver operating characteristic analyses show remarkable concordance between pyruvate's beneficial functional and metabolic effects in isolated, perfused hearts and in patients recovering from cardiopulmonary bypass in which they received pyruvate- vs. L-lactate-fortified cardioplegia. This research exemplifies the translation of mechanism-oriented preclinical studies to clinical application and outcomes.

Proteases of haematophagous arthropod vectors are involved in blood-feeding, yolk formation and immunity - a review

Ticks, triatomines, mosquitoes and sand flies comprise a large number of haematophagous arthropods considered vectors of human infectious diseases. While consuming blood to obtain the nutrients necessary to carry on life functions, these insects can transmit pathogenic microorganisms to the vertebrate host. Among the molecules related to the blood-feeding habit, proteases play an essential role. In this review, we provide a panorama of proteases from arthropod vectors involved in haematophagy, in digestion, in egg development and in immunity. As these molecules act in central biological processes, proteases from haematophagous vectors of infectious diseases may influence vector competence to transmit pathogens to their prey, and thus could be valuable targets for vectorial control.

Role of oxidative stress in epigenetic modification of MMP-9 promoter in the development of diabetic retinopathy

BACKGROUND

In the pathogenesis of diabetic retinopathy, damaged retinal mitochondria accelerate apoptosis of retinal capillary cells, and regulation of oxidative stress by manipulating mitochondrial superoxide dismutase (SOD2) protects mitochondrial homeostasis and prevents the development of diabetic retinopathy. Diabetes also activates matrix metalloproteinase-9 (MMP-9), and activated MMP-9 damages retinal mitochondria. Recent studies have shown a dynamic DNA methylation process playing an important role in regulation of retinal MMP-9 transcription in diabetes; the aim of this study is to investigate the role of oxidative stress in MMP-9 transcription.

METHODS

The effect of regulation of mitochondrial superoxide on DNA methylation of MMP-9 promoter region was investigated in retinal endothelial cells incubated in the presence or absence of a MnSOD mimetic MnTBAP, by quantifying the levels of 5 methyl cytosine (5mC) and hydroxyl-methyl cytosine (5hmC). The binding of DNA methylating, and of hydroxymenthylating enzymes (Dnmts and Tets, respectively), at MMP-9 promoter (by chromatin immunoprecipitation) was also evaluated. The in vitro results were confirmed in the retina of diabetic mice overexpressing SOD2.

RESULTS

MnTBAP attenuated glucose-induced decrease in 5mC levels and increase on Dnmt1 binding at the MMP-9 promoter region. MnTBAP also ameliorated alterations in 5hmC levels and Tet binding, regulated MMP-9 transcription, and prevented mitochondrial damage. Similarly, mice overexpressing SOD2 were protected from diabetes-induced alteration in MMP-9 promoter methylation, and its transcription.

CONCLUSIONS

Thus, regulation of oxidative stress by pharmacologic/genetic approaches maintains retinal mitochondrial homeostasis by ameliorating epigenetic modifications in the MMP-9 promoter region.

Processing of Snake Venom Metalloproteinases: Generation of Toxin Diversity and Enzyme Inactivation

Snake venom metalloproteinases (SVMPs) are abundant in the venoms of vipers and rattlesnakes, playing important roles for the snake adaptation to different environments, and are related to most of the pathological effects of these venoms in human victims. The effectiveness of SVMPs is greatly due to their functional diversity, targeting important physiological proteins or receptors in different tissues and in the coagulation system. Functional diversity is often related to the genetic diversification of the snake venom. In this review, we discuss some published evidence that posit that processing and post-translational modifications are great contributors for the generation of functional diversity and for maintaining latency or inactivation of enzymes belonging to this relevant family of venom toxins.

Acute exacerbations of COPD are associated with significant activation of matrix metalloproteinase 9 irrespectively of airway obstruction, emphysema and infection

Background

Acute exacerbations of chronic obstructive pulmonary disease (AE-COPD) are associated with accelerated aggravation of clinical symptoms and deterioration of pulmonary function. The mechanisms by which exacerbations may contribute to airway remodeling and declined lung function are poorly understood. In this study, we investigated if AE-COPD are associated with differential expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in bronchoalveolar lavage (BAL).

Methods

COPD patients undergoing diagnostic bronchoscopy, with either stable disease (n = 53) or AE-COPD (n = 44), matched for their demographics and lung function parameters were included in this study. Protein levels of MMP-2,–9,–12 and of TIMP-1 and -2 in BAL were measured by ELISA. Enzymatic activity of MMP-2 and -9 was assessed by gelatin zymography.

Results

We observed that MMP-9, TIMP-1 and TIMP-2 were significantly increased in BAL during AE-COPD. Furthermore, there was a significant negative correlation of MMP-9, TIMP-1 and TIMP-2 with FEV1% predicted and a significant positive correlation of TIMP-1 and TIMP-2 with RV% predicted in AE-COPD. None of MMPs and TIMPs correlated with DLCO% predicted, indicating that they are associated with airway remodeling leading to obstruction rather than emphysema. In AE-COPD the gelatinolytic activity of MMP-2 was increased and furthermore, MMP-9 activation was significantly up-regulated irrespective of lung function, bacterial or viral infections and smoking.

Conclusions

The results of this study indicate that during AE-COPD increased expression of TIMP-1, TIMP-2, and MMP-9 and activation of MMP-9 may be persistent aggravating factors associated with airway remodeling and obstruction, suggesting a pathway connecting frequent exacerbations to lung function decline.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0240-4) contains supplementary material, which is available to authorized users.

TLR2 and AP-1/NF-kappaB are involved in the regulation of MMP-9 elicited by heat killed Listeria monocytogenes in human monocytic THP-1 cells

BACKGROUND

MMP-9 is crucial for a normal immune response, but excessive release of this enzyme leads to severe tissue damage. Listeria monocytogenes (LM) is an opportunistic food-borne pathogen causing listerosis, meningitis and sepsis. Heat killed Listeria monocytogenes (HKLM) activates immune system and leads production of cytokines and chemokines. However, nothing is known about the involvement of HKLM in MMP-9 regulation. Therefore we investigated the role of HKLM in the regulation of MMP-9 gene expression in THP-1 cells.

METHODS

Commercially available heat killed Listeria monocytogenes was used in this study. HKLM-induced MMP-9 expression was assessed with quantitative real-time qPCR and ELISA. Action of HKLM in different signaling pathways were studied by using THP-1-XBlue™ cells (THP-1-cells with NF-κB/AP-1 reporter construct), THP-1-XBlue™-defMyD cells (MyD88(-/-) THP-1 cells), anti-TLR2 mAb and pharmacological inhibitors. Phospho and total proteins were determined by Western blotting.

RESULTS

Increased MMP-9 production (mRNA: 395-Fold; Protein: 8141 pg/ml; P < 0.05) was observed in HKLM stimulated THP-1 cells as compared to the un-stimulated THP-1 cells. This production of MMP-9 was completely abrogated by anti-TLR2 blocking mAb (P = 0.0024). Furthermore, THP-1-XBlue™-defMyD cells were unable to produce MMP-9 in response to HKLM. HKLM- induced activation of NF-kappaB/AP-1 was also observed in THP-1-XBlue™ Cells. In addition, inhibitors of JNK (SP600125), MEK/ERK (U0126; PD98056), p38 MAPK (SB203580) and NF-kappaB (BAY 11-7085, Triptolide and Resveratrol) significantly suppressed (P < 0.05) HKLM-stimulated MMP-9 expression.

CONCLUSION

Our results indicate that HKLM activates TLR2 and NF-κB/AP-1 signaling pathways, leading to up-regulation of MMP-9 production in THP-1 cells. Thus, MMP-9 could be an appropriate therapeutic target to stop severe tissue damage caused by infection or chronic inflammation.

Dihydrolipoic but not alpha-lipoic acid affects susceptibility of eukaryotic cells to bacterial invasion

Sensitivity of eukaryotic cells to facultative pathogens can depend on physiological state of host cells. Previously we have shown that pretreatment of HeLa cells with N-acetylcysteine (NAC) makes the cells 2-3-fold more sensitive to invasion by the wild-type Serratia grimesii and recombinant Escherichia coli expressing gene of actin-specific metalloprotease grimelysin [1]. To evaluate the impact of chemically different antioxidants, in the present work we studied the effects of α-Lipoic acid (LA) and dihydrolipoic acid (DHLA) on efficiency of S. grimesii and recombinant E. coli expressing grimelysin gene to penetrate into HeLa and CaCo cells. Similarly to the effect of NAC, pretreatment of HeLa and CaCo cells with 0.6 or 1.25 mM DHLA increased the entry of grimelysin producing bacteria by a factor of 2.5 and 3 for the wild-type S. grimesii and recombinant E. coli, respectively. In contrast, pretreatment of the cells with 0.6 or 1.25 mM LA did not affect the bacteria uptake. The increased invasion of HeLa and CaCo cells correlated with the enhanced expression of E-cadherin and β-catenin genes, whereas expression of these genes in the LA-treated cells was not changed. Comparison of these results suggests that it is sulfhydryl group of DHLA that promotes efficient modification of cell properties assisting bacterial uptake. We assume that the NAC- and DHLA-induced stimulation of the E-cadherin-catenin pathway contributes to the increased internalization of the grimelysin producing bacteria within transformed cells.

Hyperbaric oxygen, vasculogenic stem cells, and wound healing

SIGNIFICANCE

Oxidative stress is recognized as playing a role in stem cell mobilization from peripheral sites and also cell function.

RECENT ADVANCES

This review focuses on the impact of hyperoxia on vasculogenic stem cells and elements of wound healing.

CRITICAL ISSUES

Components of the wound-healing process in which oxidative stress has a positive impact on the various cells involved in wound healing are highlighted. A slightly different view of wound-healing physiology is adopted by departing from the often used notion of sequential stages: hemostatic, inflammatory, proliferative, and remodeling and instead organizes the cascade of wound healing as overlapping events or waves pertaining to reactive oxygen species, lactate, and nitric oxide. This was done because hyperoxia has effects of a number of cell signaling events that converge to influence cell recruitment/chemotaxis and gene regulation/protein synthesis responses which mediate wound healing.

FUTURE DIRECTIONS

Our alternative perspective of the stages of wound healing eases recognition of the multiple sites where oxidative stress has an impact on wound healing. This aids the focus on mechanistic events and the interplay among various cell types and biochemical processes. It also highlights the areas where additional research is needed.

Functional characterization of Anopheles matrix metalloprotease 1 reveals its agonistic role during sporogonic development of malaria parasites

The ability to invade tissues is a unique characteristic of the malaria stages that develop/differentiate within the mosquitoes (ookinetes and sporozoites). On the other hand, tissue invasion by many pathogens has often been associated with increased matrix metalloprotease (MMP) activity in the invaded tissues. By employing cell biology and reverse genetics, we studied the expression and explored putative functions of one of the three MMPs encoded in the genome of the malaria vector Anopheles gambiae, namely, the Anopheles gambiae MMP1 (AgMMP1) gene, during the processes of blood digestion, midgut epithelium invasion by Plasmodium ookinetes, and oocyst development. We show that AgMMP1 exists in two alternative isoforms resulting from alternative splicing; one secreted (S-MMP1) and associated with hemocytes, and one membrane type (MT-MMP1) enriched in the cell attachment sites of the midgut epithelium. MT-MMP1 showed a remarkable response to ookinete midgut invasion manifested by increased expression, enhanced zymogen maturation, and subcellular redistribution, all indicative of an implication in the midgut epithelial healing that accompanies ookinete invasion. Importantly, RNA interference (RNAi)-mediated silencing of the AgMMP1 gene revealed a postinvasion protective function of AgMMP1 during oocyst development. The combined results link for the first time an MMP with vector competence and mosquito-Plasmodium interactions.

Erythropoietin: powerful protection of ischemic and post-ischemic brain

Ischemic brain injury inflicted by stroke and cardiac arrest ranks among the leading causes of death and long-term disability in the United States. The brain consumes large amounts of metabolic substrates and oxygen to sustain its energy requirements. Consequently, the brain is exquisitely sensitive to interruptions in its blood supply, and suffers irreversible damage after 10-15 min of severe ischemia. Effective treatments to protect the brain from stroke and cardiac arrest have proven elusive, due to the complexities of the injury cascades ignited by ischemia and reperfusion. Although recombinant tissue plasminogen activator and therapeutic hypothermia have proven efficacious for stroke and cardiac arrest, respectively, these treatments are constrained by narrow therapeutic windows, potentially detrimental side-effects and the limited availability of hypothermia equipment. Mounting evidence demonstrates the cytokine hormone erythropoietin (EPO) to be a powerful neuroprotective agent and a potential adjuvant to established therapies. Classically, EPO originating primarily in the kidneys promotes erythrocyte production by suppressing apoptosis of proerythroid progenitors in bone marrow. However, the brain is capable of producing EPO, and EPO's membrane receptors and signaling components also are expressed in neurons and astrocytes. EPO activates signaling cascades that increase the brain's resistance to ischemia-reperfusion stress by stabilizing mitochondrial membranes, limiting formation of reactive oxygen and nitrogen intermediates, and suppressing pro-inflammatory cytokine production and neutrophil infiltration. Collectively, these mechanisms preserve functional brain tissue and, thus, improve neurocognitive recovery from brain ischemia. This article reviews the mechanisms mediating EPO-induced brain protection, critiques the clinical utility of exogenous EPO to preserve brain threatened by ischemic stroke and cardiac arrest, and discusses the prospects for induction of EPO production within the brain by the intermediary metabolite, pyruvate.

Clinical and immunological aspects of post-kala-azar dermal leishmaniasis in Bangladesh

We conducted active surveillance for kala-azar and post-kala-azar dermal leishmaniasis (PKDL) in a population of 24,814 individuals. Between 2002 and 2010, 1,002 kala-azar and 185 PKDL cases occurred. Median PKDL patient age was 12 years; 9% had no antecedent kala-azar. Cases per 10,000 person-years peaked at 90 for kala-azar (2005) and 28 for PKDL (2007). Cumulative PKDL incidence among kala-azar patients was 17% by 5 years. Kala-azar patients younger than 15 years were more likely than older patients to develop PKDL; no other risk factors were identified. The most common lesions were hypopigmented macules. Of 98 untreated PKDL patients, 48 (49%) patients had resolution, with median time of 19 months. Kala-azar patients showed elevated interferon-γ (IFNγ), tumor necrosis factor-α (TNFα), and interleukin 10 (IL-10). Matrix metalloproteinase 9 (MMP9) and MMP9/tissue inhibitor of matrix metalloproteinase-1 (TIMP1) ratio were significantly higher in PKDL patients than in other groups. PKDL is frequent in Bangladesh and poses a challenge to the current visceral leishmaniasis elimination initiative in the Indian subcontinent.

Preventive and prophylactic mechanisms of action of pomegranate bioactive constituents

Pomegranate fruit presents strong anti-inflammatory, antioxidant, antiobesity, and antitumoral properties, thus leading to an increased popularity as a functional food and nutraceutical source since ancient times. It can be divided into three parts: seeds, peel, and juice, all of which seem to have medicinal benefits. Several studies investigate its bioactive components as a means to associate them with a specific beneficial effect and develop future products and therapeutic applications. Many beneficial effects are related to the presence of ellagic acid, ellagitannins (including punicalagins), punicic acid and other fatty acids, flavonoids, anthocyanidins, anthocyanins, estrogenic flavonols, and flavones, which seem to be its most therapeutically beneficial components. However, the synergistic action of the pomegranate constituents appears to be superior when compared to individual constituents. Promising results have been obtained for the treatment of certain diseases including obesity, insulin resistance, intestinal inflammation, and cancer. Although moderate consumption of pomegranate does not result in adverse effects, future studies are needed to assess safety and potential interactions with drugs that may alter the bioavailability of bioactive constituents of pomegranate as well as drugs. The aim of this review is to summarize the health effects and mechanisms of action of pomegranate extracts in chronic inflammatory diseases.

Human pathogens utilize host extracellular matrix proteins laminin and collagen for adhesion and invasion of the host

Laminin (Ln) and collagen are multifunctional glycoproteins that play an important role in cellular morphogenesis, cell signalling, tissue repair and cell migration. These proteins are ubiquitously present in tissues as a part of the basement membrane (BM), constitute a protective layer around blood capillaries and are included in the extracellular matrix (ECM). As a component of BMs, both Lns and collagen(s), thus function as major mechanical containment molecules that protect tissues from pathogens. Invasive pathogens breach the basal lamina and degrade ECM proteins of interstitial spaces and connective tissues using various ECM-degrading proteases or surface-bound plasminogen and matrix metalloproteinases recruited from the host. Most pathogens associated with the respiratory, gastrointestinal, or urogenital tracts, as well as with the central nervous system or the skin, have the capacity to bind and degrade Lns and collagen(s) in order to adhere to and invade host tissues. In this review, we focus on the adaptability of various pathogens to utilize these ECM proteins as enhancers for adhesion to host tissues or as a targets for degradation in order to breach the cellular barriers. The major pathogens discussed are Streptococcus, Staphylococcus, Pseudomonas, Salmonella, Yersinia, Treponema, Mycobacterium, Clostridium, Listeria, Porphyromonas and Haemophilus; Candida, Aspergillus, Pneumocystis, Cryptococcus and Coccidioides; Acanthamoeba, Trypanosoma and Trichomonas; retrovirus and papilloma virus.

Zinc metalloproteinase ProA directly activates Legionella pneumophila PlaC glycerophospholipid:cholesterol acyltransferase

Enzymes secreted by Legionella pneumophila, such as phospholipases A (PLAs) and glycerophospholipid:cholesterol acyltransferases (GCATs), may target host cell lipids and therefore contribute to the establishment of Legionnaires disease. L. pneumophila possesses three proteins, PlaA, PlaC, and PlaD, belonging to the GDSL family of lipases/acyltransferases. We have shown previously that PlaC is the major GCAT secreted by L. pneumophila and that the zinc metalloproteinase ProA is essential for GCAT activity. Here we characterized the mode of PlaC GCAT activation and determined that ProA directly processes PlaC. We further found that not only cholesterol but also ergosterol present in protozoa was palmitoylated by PlaC. Such ester formations were not induced by either PlaA or PlaD. PlaD was shown here to possess lysophospholipase A activity, and interestingly, all three GDSL enzymes transferred short chain fatty acids to sterols. The three single putative catalytic amino acids (Ser-37, Asp-398, and His-401) proved essential for all PlaC-associated PLA, lysophospholipase A, and GCAT activities. A further four cysteine residues are important for the PLA/GCAT activities as well as their oxidized state, and we therefore conclude that PlaC likely forms at least one disulfide loop. Analysis of cleavage site and loop deletion mutants suggested that for GCAT activation deletion of several amino acids within the loop is necessary rather than cleavage at a single site. Our data therefore suggest a novel enzyme inhibition/activation mechanism where a disulfide loop inhibits PlaC GCAT activity until the protein is exported to the external space where it is ProA-activated.

Nitric oxide modulates metalloproteinase-2, collagen deposition and adhesion rate after polypropylene mesh implantation in the intra-abdominal wall

Prosthetic meshes are commonly used to correct abdominal wall defects. However, the inflammatory reaction induced by these devices in the peritoneum is not completely understood. We hypothesized that nitric oxide (NO), produced by nitric oxide synthase 2 (NOS2) may modulate the response induced by mesh implants in the abdominal wall and, consequently, affect the outcome of the surgical procedure. Polypropylene meshes were implanted in the peritoneal side of the abdominal wall in wild-type and NOS2-deficient (NOS2(-/-)) mice. After 15 days tissues around the mesh implant were collected, and inflammatory markers (the cytokine interleukin 1β (IL-1β) and NO) and tissue remodeling (collagen and metalloproteinases (MMP) 2 and 9) were analyzed. The lack of NOS2-derived NO induced a higher incidence of visceral adhesions at the mesh implantation site compared with wild-type mice that underwent the same procedure (P<0.05). Additionally, higher levels of IL-1β were present in the mesh-implanted NOS2(-/-) animals compared with control and wild-type mice. Mesh implantation induced collagen I and III deposition, but in smaller amounts in NOS2(-/-) mice. MMP-9 activity after the surgical procedure was similarly increased in both groups. Conversely, MMP-2 activity was unchanged in mesh-implanted wild-type mice, but was significantly increased in NOS2(-/-) mice (P<0.01), due to decreased S-nitrosylation of the enzyme in these animals. We conclude that NOS2-derived NO is crucial for an adequate response to and integration of polypropylene mesh implants in the peritoneum. NO deficiency results in a prolonged inflammatory reaction to the mesh implant, and reduced collagen deposition may contribute to an increased incidence of visceral adhesions.

Increase of nitrosative stress in patients with eosinophilic pneumonia

Background

Exhaled nitric oxide (NO) production is increased in asthma and reflects the degree of airway inflammation. The alveolar NO concentration (Calv) in interstitial pneumonia is reported to be increased. However, it remains unknown whether NO production is increased and nitrosative stress occurs in eosinophilic pneumonia (EP). We hypothesized that nitrosative stress markers including Calv, inducible type of NO synthase (iNOS), and 3-nitrotyrosine (3-NT), are upregulated in EP.

Methods

Exhaled NO including fractional exhaled NO (FE_NO) and Calv was measured in ten healthy subjects, 13 patients with idiopathic pulmonary fibrosis (IPF), and 13 patients with EP. iNOS expression and 3-NT formation were assessed by immunocytochemistory in BALf cells. The exhaled NO, lung function, and systemic inflammatory markers of the EP patients were investigated after corticosteroid treatment for 4 weeks.

Results

The Calv levels in the EP group (14.4 ± 2.0 ppb) were significantly higher than those in the healthy subjects (5.1 ± 0.6 ppb, p < 0.01) and the IPF groups (6.3 ± 0.6 ppb, p < 0.01) as well as the FE_NO and the corrected Calv levels (all p < 0.01). More iNOS and 3-NT positive cells were observed in the EP group compared to the healthy subject and IPF patient. The Calv levels had significant positive correlations with both iNOS (r = 0.858, p < 0.05) and 3-NT positive cells (r = 0.924, p < 0.01). Corticosteroid treatment significantly reduced both the FE_NO (p < 0.05) and the Calv levels (p < 0.01). The magnitude of reduction in the Calv levels had a significant positive correlation with the peripheral blood eosinophil counts (r = 0.802, p < 0.05).

Conclusions

These results suggested that excessive nitrosative stress occurred in EP and that Calv could be a marker of the disease activity.

Infection with human coronavirus NL63 enhances streptococcal adherence to epithelial cells

Understanding the mechanisms of augmented bacterial pathogenicity in post-viral infections is the first step in the development of an effective therapy. This study assessed the effect of human coronavirus NL63 (HCoV-NL63) on the adherence of bacterial pathogens associated with respiratory tract illnesses. It was shown that HCoV-NL63 infection resulted in an increased adherence of Streptococcus pneumoniae to virus-infected cell lines and fully differentiated primary human airway epithelium cultures. The enhanced binding of bacteria correlated with an increased expression level of the platelet-activating factor receptor (PAF-R), but detailed evaluation of the bacterium-PAF-R interaction revealed a limited relevance of this process.

Bacterial invasion of eukaryotic cells can be mediated by actin-hydrolysing metalloproteases grimelysin and protealysin

Earlier, we have shown that spontaneously isolated non-pathogenic bacteria Serratia grimesii and Serratia proteamaculans invade eukaryotic cells, provided that they synthesize thermolysin-like metalloproteases ECP32/grimelysin or protealysin characterized by high specificity towards actin. To address the question of whether the proteases are active players in entry of these bacteria into host cells, in this work, human larynx carcinoma Hep-2 cells were infected with recombinant Escherichia coli expressing grimelysin or protealysin. Using confocal and electron microscopy, we have found that the recombinant bacteria, whose extracts limitedly cleaved actin, were internalized within the eukaryotic cells residing both in vacuoles and free in cytoplasm. The E. coli-carrying plasmids without inserts of grimelysin or protealysin gene did not enter Hep-2 cells. Moreover, internalization of non-invasive E. coli was not observed in the presence of protealysin introduced into the culture medium. These results are consistent with the direct participation of ECP32/grimelysin and protealysin in entry of bacteria into the host cells. We assume that ECP32/grimelysin and protealysin mediate invasion being injected into the eukaryotic cell and that the high specificity of the enzyme towards actin may be a factor contributed to the bacteria internalization.

A first study on the usefulness of matrix metalloproteinase 9 from dentinal fluid to indicate pulp inflammation

INTRODUCTION

Pulpal diagnostics might be improved by using molecular markers found in dentinal fluid. In the current pilot study, we tested whether matrix metallopeptidase 9 (MMP-9) levels in dentinal fluid were detectable and differed between pulps from symptomatic teeth diagnosed with irreversible pulpitis and healthy counterparts.

METHODS

Thirty-one patients participated; 19 were diagnosed with irreversible pulpitis, and 12 were in need of replacement of a filling close to the pulp space in a clinically healthy tooth. Dentinal fluid was collected during a period of 2 minutes from dentin cavities by using folded polyvinylidene difluoride (PVDF) membranes, which were then transferred to microcentrifugation tubes containing physiologic saline solution. Total MMP-9 levels in these solutions were assessed by using a human MMP-9 fluorescent assay, detection limit 0.25 ng/mL. MMP-9 levels between groups were compared by using Mann-Whitney U test (alpha <0.05).

RESULTS

Three specimens from the symptomatic teeth were not included because coronal pulps proved to be necrotic on access. Dentinal fluid samples from symptomatic teeth had significantly higher MMP-9 levels than those from clinically healthy counterparts (P < .05). However, merely 7 of the 16 pulpitis samples contained detectable levels of MMP-9. None of the clinically healthy control specimens contained any detectable amounts of MMP-9.

CONCLUSIONS

With a sensitive assay, it was possible to detect an enzyme linked with pulp tissue destruction (MMP-9) in dentinal fluid. However, the collection method needs to be improved to provide predictable fluid yields. Longitudinal studies should be performed to assess the predictive value of molecular markers in dentinal fluid on pulpal pathosis.

Multiple roles of metalloproteinases in neurological disorders

Once thought to mainly act in brain to remodel the extracellular matrix, the family of metalloproteinases is important in many normal and pathological processes in the nervous system. Matrix metalloproteinases (MMPs) and A disintegrin and metalloproteinases (ADAMs) are the two major families of metalloproteinases in the brain. MMPs are comprised of several related enzymes that act on extracellular molecules. Normally, they are important in angiogenesis and neurogenesis in development. In neuroinflammatory illnesses, they disrupt the basal lamina and tight junction proteins to open the blood-brain barrier (BBB). ADAMs are important in neuroinflammation through activation of tumor necrosis factor-α (TNF-α) and their action as secretases that modulate the action of receptors on the cell surface. Four tissue inhibitors of metalloproteinases (TIMPs) are the main inhibitors of the MMPs and ADAMs. Recently, MMPs were found to affect DNA repair processes by an unexpected intranuclear action. MMPs and ADAMs have been implicated in the pathophysiology of neurodegenerative diseases such as Alzheimer's disease and vascular cognitive impairment. Growing literature on the functions of MMPs and ADAMs in the central nervous system is opening up new and exciting areas of research that may lead to novel approaches to treatment of neurological diseases.

Interaction between endometrial epithelial cells and blood leucocytes promotes cytokine release and epithelial barrier function in response to Chlamydia trachomatis lipopolysaccharide stimulation

Chlamydia trachomatis infection is currently the most common cause of infection-related sterility in women. However, it remains largely unknown how uterine epithelial cells interact with recruited leucocytes in response to C. trachomatis infection in the female genital tract. To study the defence mechanism of the endometrium against C. trachomatis infection, we established an in vitro co-culture of EEC (endometrial epithelial cells) and PBL (peripheral blood leucocytes) isolated from mice and investigated the immune response of these cells upon C. trachomatis LPS (lipopolysaccharide) challenge using a cytokine antibody array and RT-PCR (reverse transcription-PCR). Our results showed that upon C. trachomatis LPS stimulation, proinflammatory cytokines/chemokines, such as TNF-alpha, IL-1beta, MIPs (macrophage inflammatory proteins), IL-12p40p70, KC, GCSFs (granulocyte colony stimulating factors), IL-6 and TIMPs (tissue inhibition metalloproteinases) are up-regulated and/or released from EEC-PBL co-culture. Further, the TER (transepithelial resistance), measured by the Isc (short-circuit current) technique was significantly increased in EEC/PBL co-cultured cells and also when stimulated with C. trachomatis LPS compared with EEC alone. These changes appear to be mediated by the change in cytokine-induced expression of tight junction-related protein ZO-1. The present results demonstrated that the epithelial-immune cross-talk could promote the release of proinflammatory cytokines and enhance the barrier function of the endometrium against C. trachomatis infection in the female reproductive tract.

Pyruvate-enriched cardioplegia suppresses cardiopulmonary bypass-induced myocardial inflammation

BACKGROUND

Cardiopulmonary bypass-induced oxidative stress initiates inflammation that can damage the myocardium. This study tested whether cardioplegia enriched with the intermediary metabolite and antioxidant pyruvate dampens postbypass myocardial inflammation.

METHODS

Pigs were maintained on cardiopulmonary bypass while their hearts were arrested for 60 minutes with 4:1 blood:crystalloid cardioplegia, in which the crystalloid contained 188 mM glucose ± 24 mM pyruvate. Pigs were weaned from bypass after 30 minutes of whole blood reperfusion and recovered for 4 hours. Glutathione (GSH) and glutathione disulfide (GSSG) were measured in coronary sinus plasma to indirectly monitor myocardial GSH redox state (GSH/GSSG). Left ventricular myocardium was sampled 4 hours after cardiopulmonary bypass for analyses of C-reactive protein, matrix metalloproteinases 2 and 9 and tissue inhibitor of metalloproteinase-2 (TIMP-2), and to assess neutrophil infiltration by histology and myeloperoxidase assay.

RESULTS

Coronary sinus GSH/GSSG fell 70% after cardiopulmonary bypass with control cardioplegia, but pyruvate cardioplegia produced a robust increase in coronary sinus GSH/GSSG that persisted for 4 hours after bypass. Myocardial C-reactive protein content increased 5.6-fold after control bypass, and neutrophil infiltration and myeloperoxidase activity also increased, but pyruvate-fortified cardioplegia prevented these inflammatory effects. Control cardioplegia lowered myocardial TIMP-2 content by 59% and increased matrix metalloproteinase-9 activity by 35% versus nonbypass sham values, but pyruvate cardioplegia increased TIMP-2 content ninefold versus control cardioplegia and prevented the increase in matrix metalloproteinase-9. Matrix metalloproteinase-2 was not affected by bypass ± pyruvate.

CONCLUSIONS

Pyruvate-enriched cardioplegia dampens cardiopulmonary bypass-induced myocardial inflammation. Increased GSH/GSSG and TIMP-2 may mediate pyruvate's effects.

Granulocyte-macrophage colony-stimulating factor- and tumor necrosis factor alpha-mediated matrix metalloproteinase production by human osteoblasts and monocytes after infection with Brucella abortus

Osteoarticular complications are common in human brucellosis, but the pathogenic mechanisms involved are largely unknown. Since matrix metalloproteinases (MMPs) are involved in joint and bone damage in inflammatory and infectious diseases, we investigated the production of MMPs by human osteoblasts and monocytes, either upon Brucella abortus infection or upon reciprocal stimulation with factors produced by each infected cell type. B. abortus infection of the normal human osteoblastic cell line hFOB 1.19 triggered a significant release of MMP-2, which was mediated in part by granulocyte-macrophage colony-stimulating factor (GM-CSF) acting on these same cells. Supernatants from infected osteoblasts exhibited increased levels of monocyte chemoattractant protein 1 and induced the migration of human monocytes (THP-1 cell line). Infection with B. abortus induced a high MMP-9 secretion in monocytes, which was also induced by heat-killed B. abortus and by the Omp19 lipoprotein from B. abortus. These effects were mediated by Toll-like receptor 2 and by the action of tumor necrosis factor alpha (TNF-α) produced by these same cells. Supernatants from B. abortus-infected monocytes induced MMP-2 secretion in uninfected osteoblasts, and this effect was mediated by TNF-α. Similarly, supernatants from infected osteoblasts induced MMP-9 secretion in uninfected monocytes. This effect was mediated by GM-CSF, which induced TNF-α production by monocytes, which in turn induced MMP-9 in these cells. These results suggest that MMPs could be potentially involved in the tissue damage observed in osteoarticular brucellosis.

Protein oxidation: role in signalling and detection by mass spectrometry

Proteins can undergo a wide variety of oxidative post-translational modifications (oxPTM); while reversible modifications are thought to be relevant in physiological processes, non-reversible oxPTM may contribute to pathological situations and disease. The oxidant is also important in determining the type of oxPTM, such as oxidation, chlorination or nitration. The best characterized oxPTMs involved in signalling modulation are partial oxidations of cysteine to disulfide, glutathionylated or sulfenic acid forms that can be reversed by thiol reductants. Proline hydroxylation in HIF signalling is also quite well characterized, and there is increasing evidence that specific oxidations of methionine and tyrosine may have some biological roles. For some proteins regulated by cysteine oxidation, the residues and molecular mechanism involved have been extensively studied and are well understood, such as the protein tyrosine phosphatase PTP1B and MAP3 kinase ASK1, as well as transcription factor complex Keap1-Nrf2. The advances in understanding of the role oxPTMs in signalling have been facilitated by advances in analytical technology, in particular tandem mass spectrometry techniques. Combinations of peptide sequencing by collisionally induced dissociation and precursor ion scanning or neutral loss to select for specific oxPTMs have proved very useful for identifying oxidatively modified proteins and mapping the sites of oxidation. The development of specific labelling and enrichment procedures for S-nitrosylation or disulfide formation has proved invaluable, and there is ongoing work to establish analogous methods for detection of nitrotyrosine and other modifications.

Equine laminitis: ultrastructural lesions detected 24-30 hours after induction with oligofructose

REASONS FOR PERFORMING STUDY

The pathology of equine laminitis has been well-documented 48 h after dosing with oligofructose when clinical lameness and lamellar disintegration is well advanced. Further analysis of the earliest lesions, by collecting lamellar samples at the first sign of foot lameness after oligofructose dosing is required in order to increase understanding of the disease.

OBJECTIVES

To investigate lamellar epidermal hemidesmosome damage and basement membrane dysadhesion by transmission electron microscopy (TEM).

METHODS

Eight clinically normal, mature Standardbred horses were divided randomly into 2 groups of 4. The treatment group were dosed with oligofructose (10 g/kg bwt) and subjected to euthanasia when shifting weight from one foot to other commenced and at the first sign of lameness during walking and turning. This occurred at 24 h in 3 horses and 30 h in one. The sham treatment control group were dosed with water and subjected to euthanasia after 48 h. Lamellar tissues of the front feet were harvested and processed for ultrastructural study using TEM.

RESULTS

Examination by TEM showed excessive waviness of the basement membrane zone and pointed tips of some secondary epidermal lamellae, an ultrastructural lesion typical of laminitis. The average number of hemidesmosomes/microm of basement membrane was decreased and their distance from the centre of the lamina densa of the basement membrane was increased.

CONCLUSIONS

Laminitis lesions are detectable 24 h after oligofructose administration.

POTENTIAL RELEVANCE

Hindgut events occurring in the first 24 h after dosing have begun the destruction of the hoof lamellar interface. Prevention and treatment strategies should precede lameness if they are to be efficacious.

Alcohol, signaling, and ECM turnover

Alcohol is recognized as a direct hepatotoxin, but the precise molecular pathways that are important for the initiation and progression of alcohol-induced tissue injury are not completely understood. The current understanding of alcohol toxicity to organs suggests that alcohol initiates injury by generation of oxidative and nonoxidative ethanol metabolites and via translocation of gut-derived endotoxin. These processes lead to cellular injury and stimulation of the inflammatory responses mediated through a variety of molecules. With continuing alcohol abuse, the injury progresses through impairment of tissue regeneration and extracellular matrix (ECM) turnover, leading to fibrogenesis and cirrhosis. Several cell types are involved in this process, the predominant being stellate cells, macrophages, and parenchymal cells. In response to alcohol, growth factors and cytokines activate many signaling cascades that regulate fibrogenesis. This mini-review brings together research focusing on the underlying mechanisms of alcohol-mediated injury in a number of organs. It highlights the various processes and molecules that are likely involved in inflammation, immune modulation, susceptibility to infection, ECM turnover and fibrogenesis in the liver, pancreas, and lung triggered by alcohol abuse.

High matrix metalloproteinase production correlates with immune activation and leukocyte migration in leprosy reactional lesions

Gelatinases A and B (matrix metalloproteinase 2 [MMP-2] and MMP-9, respectively) can induce basal membrane breakdown and leukocyte migration, but their role in leprosy skin inflammation remains unclear. In this study, we analyzed clinical specimens from leprosy patients taken from stable, untreated skin lesions and during reactional episodes (reversal reaction [RR] and erythema nodosum leprosum [ENL]). The participation of MMPs in disease was suggested by (i) increased MMP mRNA expression levels in skin biopsy specimens correlating with the expression of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha), (ii) the detection of the MMP protein and enzymatic activity within the inflammatory infiltrate, (iii) increased MMP levels in patient sera, and (iv) the in vitro induction of MMP-9 by Mycobacterium leprae and/or TNF-alpha. It was observed that IFN-gamma, TNF-alpha, MMP-2, and MMP-9 mRNA levels were higher in tuberculoid than lepromatous lesions. In contrast, interleukin-10 and tissue inhibitor of MMP (TIMP-1) message were not differentially modulated. These data correlated with the detection of the MMP protein evidenced by immunohistochemistry and confocal microscopy. When RR and ENL lesions were analyzed, an increase in TNF-alpha, MMP-2, and MMP-9, but not TIMP-1, mRNA levels was observed together with stronger MMP activity (zymography/in situ zymography). Moreover, following in vitro stimulation of peripheral blood cells, M. leprae induced the expression of MMP-9 (mRNA and protein) in cultured cells. Overall, the present data demonstrate an enhanced MMP/TIMP-1 ratio in the inflammatory states of leprosy and point to potential mechanisms for tissue damage. These results pave the way toward the application of new therapeutic interventions for leprosy reactions.

Acute pancreatitis: hypertonic saline increases heat shock proteins 70 and 90 and reduces neutrophil infiltration in lung injury

OBJECTIVES

Acute pancreatitis (AP) protease release induces lung parenchymal destruction via matrix metalloproteinases (MMPs), a neutrophil (polymorphonuclear leukocyte)-dependent process. Recent studies in hemorrhagic shock revealed that hypertonic saline (HTS) has an anti-inflammatory effect and can inhibit a variety of neutrophil functions. The aim of this study was to determine whether HTS and its actions in the pathway of neutrophil migration, MMPs, and heat shock proteins (HSPs) are effective in protecting the lung from injury associated with AP.

METHODS

We determined neutrophil infiltration and expressions of MMPs and HSPs in the lung tissue after AP induced by retrograde infusion of 2.5% of sodium taurocholate.

RESULTS

Animals submitted to AP that received HTS compared with those who received normal saline presented with increased HSP70 and HSP90 expressions and reduced myeloperoxidase levels and MMP-9 expression and activity.

CONCLUSIONS

Our data raised the hypothesis that a sequence of HTS lung protection events increases HSP70 and HSP90, inhibiting infiltration of neutrophils and their protease actions in the lung.

Hypertonic saline reduces metalloproteinase expression in liver during pancreatitis

1. We recently demonstrated that hypertonic saline reduces inflammation and mortality in acute pancreatitis. The present study investigated the effects of hypertonic saline in metalloproteinase (MMP) regulation and pancreatitis-associated hepatic injury. 2. Wistar rats were divided into four groups: (i) control, not subjected to insult or treatment; (ii) no treatment (NT), induction of pancreatitis (retrograde infusion of 2.5% sodium taurocholate (1.0 mL/kg)), but no further treatment; (iii) normal saline (NS), induction of pancreatitis and treatment with normal saline (0.9% NaCl, 34 mL/kg, i.v. bolus, 1 h after the induction of pancreatitis); and (iv) hypertonic saline (HS), induction of pancreatitis and treatment with hypertonic saline (7.5% NaCl, 4 mL/kg administered over a period of 5 min, 1 h after the induction of pancreatitis). In all four groups, 4, 12 and 24 h after the induction of pancreatitis, liver tissue samples were assayed to determine levels of MMP-2, MMP-9, 47 kDa heat shock protein (HSP47) and collagen (Type I and III). 3. Compared with the control group, MMP-9 expression and activity was increased twofold in the NS and NT groups 4 and 12 h after the induction of pancreatitis, but remained at basal levels in the HS group. In contrast, MMP-2 expression was increased twofold 12 h after the induction of pancreatitis only in the NS group, whereas the expression of HSP47 was increased 4 h after the induction of pancreatitis in the NS and NT groups. Greater extracellular matrix remodelling occurred in the NS and NT groups compared with the HS group, probably as a result of the hepatic wound-healing response to repeated injury. However, the collagen content in hepatic tissue remained at basal levels in the HS group. 4. In conclusion, the results of the present study indicate that hypertonic saline is hepatoprotective and reduces hepatic remodelling, maintaining the integrity of the hepatic extracellular matrix during pancreatitis. Hypertonic saline-mediated regulation of MMP expression may have clinical relevance in pancreatitis-associated liver injury.

Inducible nitric oxide synthase deficiency impairs matrix metalloproteinase-9 activity and disrupts leukocyte migration in hepatic ischemia/reperfusion injury

Matrix metalloproteinase 9 (MMP-9) is a critical mediator of leukocyte migration in hepatic ischemia/reperfusion (I/R) injury. To test the relevance of inducible nitric oxide synthase (iNOS) expression on the regulation of MMP-9 activity in liver I/R injury, our experiments included both iNOS-deficient mice and mice treated with ONO-1714, a specific iNOS inhibitor. The inability of iNOS-deficient mice to generate iNOS-derived nitric oxide (NO) profoundly inhibited MMP-9 activity and depressed leukocyte migration in livers after I/R injury. While macrophages expressed both iNOS and MMP-9 in damaged wild-type livers, neutrophils expressed MMP-9 and were virtually negative for iNOS; however, exposure of isolated murine neutrophils and macrophages to exogenous NO increased MMP-9 activity in both cell types, suggesting that NO may activate MMP-9 in leukocytes by either autocrine or paracrine mechanisms. Furthermore, macrophage NO production through the induction of iNOS was capable of promoting neutrophil transmigration across fibronectin in a MMP-9-dependent manner. iNOS expression in liver I/R injury was also linked to liver apoptosis, which was reduced in the absence of MMP-9. These results suggest that MMP-9 activity induced by iNOS-derived NO may also lead to detachment of hepatocytes from the extracellular matrix and cell death, in addition to regulating leukocyte migration across extracellular matrix barriers. These data provide evidence for a novel mechanism by which MMP-9 can mediate iNOS-induced liver I/R injury.

PIM2 Induced COX-2 and MMP-9 expression in macrophages requires PI3K and Notch1 signaling

Activation of inflammatory immune responses during granuloma formation by the host upon infection of mycobacteria is one of the crucial steps that is often associated with tissue remodeling and breakdown of the extracellular matrix. In these complex processes, cyclooxygenase-2 (COX-2) plays a major role in chronic inflammation and matrix metalloproteinase-9 (MMP-9) significantly in tissue remodeling. In this study, we investigated the molecular mechanisms underlying Phosphatidyl-myo-inositol dimannosides (PIM2), an integral component of the mycobacterial envelope, triggered COX-2 and MMP-9 expression in macrophages. PIM2 triggers the activation of Phosphoinositide-3 Kinase (PI3K) and Notch1 signaling leading to COX-2 and MMP-9 expression in a Toll-like receptor 2 (TLR2)-MyD88 dependent manner. Notch1 signaling perturbations data demonstrate the involvement of the cross-talk with members of PI3K and Mitogen activated protein kinase pathway. Enforced expression of the cleaved Notch1 in macrophages induces the expression of COX-2 and MMP-9. PIM2 triggered significant p65 nuclear factor -κB (NF-κB) nuclear translocation that was dependent on activation of PI3K or Notch1 signaling. Furthermore, COX-2 and MMP-9 expression requires Notch1 mediated recruitment of Suppressor of Hairless (CSL) and NF-κB to respective promoters. Inhibition of PIM2 induced COX-2 resulted in marked reduction in MMP-9 expression clearly implicating the role of COX-2 dependent signaling events in driving the MMP-9 expression. Taken together, these data implicate PI3K and Notch1 signaling as obligatory early proximal signaling events during PIM2 induced COX-2 and MMP-9 expression in macrophages.

Spatially distinct production of reactive oxygen species regulates platelet activation

Platelets play a key role in hemostasis and changes in redox balance are known to alter platelet activation and aggregation. Interestingly, activation of platelets leads to production of reactive oxygen species (ROS), but the role(s) of these ROS remain unclear. Using flow cytometry and chemiluminescence, agonist-induced ROS generation was found to be spatially distinct with stimulation through the major collagen receptor GPVI inducing only intraplatelet ROS while thrombin induced production of extracellular ROS. Platelet activation by either the GPVI-selective agonist convulxin or thrombin was differentially regulated by ROS generation. Thus, surface expression of CD62P, CD40L, or activated integrin alphaIIbbeta3 was abrogated by pharmacologic antioxidants but externalization of phosphatidylserine was not inhibited. Furthermore, extracellular antioxidants SOD/catalase markedly inhibited thrombin-, but not convulxin-, induced CD62P expression and alphaIIbbeta3 activation. The data suggest that ROS selectively regulate biochemical steps in platelet activation and that distinct source(s) of ROS and discrete redox-sensitive pathway(s) may control platelet activation in response to GPVI or thrombin stimulation. Thus, targeting ROS with site-specific antioxidants may differentially regulate platelet activation via thrombin or collagen.

The chemical biology of nitric oxide: implications in cellular signaling

Nitric oxide (NO) has earned the reputation of being a signaling mediator with many diverse and often opposing biological activities. The diversity in response to this simple diatomic molecule comes from the enormous variety of chemical reactions and biological properties associated with it. In the past few years, the importance of steady-state NO concentrations has emerged as a key determinant of its biological function. Precise cellular responses are differentially regulated by specific NO concentration. We propose five basic distinct concentration levels of NO activity: cGMP-mediated processes ([NO]<1-30 nM), Akt phosphorylation ([NO] = 30-100 nM), stabilization of HIF-1alpha ([NO] = 100-300 nM), phosphorylation of p53 ([NO]>400 nM), and nitrosative stress (1 microM). In general, lower NO concentrations promote cell survival and proliferation, whereas higher levels favor cell cycle arrest, apoptosis, and senescence. Free radical interactions will also influence NO signaling. One of the consequences of reactive oxygen species generation is to reduce NO concentrations. This antagonizes the signaling of nitric oxide and in some cases results in converting a cell-cycle arrest profile to a cell survival profile. The resulting reactive nitrogen species that are generated from these reactions can also have biological effects and increase oxidative and nitrosative stress responses. A number of factors determine the formation of NO and its concentration, such as diffusion, consumption, and substrate availability, which are referred to as kinetic determinants for molecular target interactions. These are the chemical and biochemical parameters that shape cellular responses to NO. Herein we discuss signal transduction and the chemical biology of NO in terms of the direct and indirect reactions.

Redox-based regulation of signal transduction: principles, pitfalls, and promises

Oxidants are produced as a by-product of aerobic metabolism, and organisms ranging from prokaryotes to mammals have evolved with an elaborate and redundant complement of antioxidant defenses to confer protection against oxidative insults. Compelling data now exist demonstrating that oxidants are used in physiological settings as signaling molecules with important regulatory functions controlling cell division, migration, contraction, and mediator production. These physiological functions are carried out in an exquisitely regulated and compartmentalized manner by mild oxidants, through subtle oxidative events that involve targeted amino acids in proteins. The precise understanding of the physiological relevance of redox signal transduction has been hampered by the lack of specificity of reagents and the need for chemical derivatization to visualize reversible oxidations. In addition, it is difficult to measure these subtle oxidation events in vivo. This article reviews some of the recent findings that illuminate the significance of redox signaling and exciting future perspectives. We also attempt to highlight some of the current pitfalls and the approaches needed to advance this important area of biochemical and biomedical research.