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Its main function is to conjugation of different electrophilic compounds with glutathione  buy sildenafil 75mg without a prescription. Oxidatively modi fied compounds as well as lipid oxidation products sildenafil 100mg fast delivery, like 4-hydroxy-2-nonenal buy 25 mg sildenafil visa, are subjected to conjugation with glutathione. Other authors found such association and reported increased susceptibility to cancerogens among Caucasian and Afri can-American populations . Role of oxidative modifications of antioxidant and related enzymes in disease progression Many disorders related to the metabolism of transition metals, amino acids or low molecular mass reductants are known to be connected with activities of antioxidant enzymes. Disruption of iron-sulfur clusters by superoxide anion radicals or peroxynitrite leads frequently to impairment of many metabolic pathways. On the other hand, iron is a component of haem, a prosthet ic group in catalase holoenzyme. The latter is believed to be one of the most susceptible to oxidation enzymes . These assumptions demonstrate the potential of antioxidant therapy in particular cases. At some pathological states, whatever the cause of the disease, oxidative stress is seen to be a powerful exacerbating factor. Indeed, en hanced level of glucose results in higher probability of protein glycation . Impact of chemopreventive agents in the chronic degenerative diseases The available evidences indicates that individuals with chronic degenerative diseases are more susceptible to oxidative stress and damage because they have elevated levels of oxi dants and/or reduced antioxidants. Therefore, it has been posited that antioxidant supple mentation in such individuals may be beneficial. Different research has confirmed that many common foods contain nonnutritive components that may provide protection against chronic degenerative diseases, however, the most studies have had impact on the cancer [20,21]. The "chemoprevention" seeks to eliminate precancerous cells in order to avoid the necessity of chemotherapy. Primary chemoprevention focuses on preventing the development of precancerous lesions, secondary chemoprevention focuses on preventing the progression of these lesions to can cer, and tertiary chemoprevention aims to prevent the recurrence or spread of a primary cancer . In vestigations of last decades, has focused on the existence of a number of non nutritional components in our regular diet that possess antimutagenic and anticarcinogenic properties, these compounds have been called as chemopreventers [76,77]. The chemopreventers are classified as food entities that can prevent the appearance of some long-term diseases like cancer or cardiovascular disorders. It has been suggested that che moprevention should be considered as an inexpensive, easily applicable approach to cancer control and "may become a major weapon in the anticancer arsenal" [76,78,79]. The mechanisms of action of the chemopreventers are complex and can be categorized ac cording to the site of action or by the specific type of action. As such, they may scavenge free radicals formed during the preparation of food or as a normal biological process in the body. Therefore, any event that removes free radicals in the human body is considered beneficial for human health. In addition to their antioxidative activities, there are other mechanisms that show in the Table 2 [80-82]. Chemopreventive evidence of some fruits and food supplements evaluated by our research group 5. The cactus pear (also called prickly pears) is the fruit of this plant (Opuntia spp. The fruit is an oval berry with a large number of seeds and a semi-hard rind with thorns, which may be grouped by fruit colors: red, purple, orange-yellow and white. The fruits with white pulp and green rind are preferred for consumption as food, and their domestic production corre sponds to almost 95% of the total production. Mexico is the main producer of cactus pears and accounts for more than 45% of the worldwide production; however, only 1. Other mechanisms of chemoprevention A viable strategy to increase the competitiveness of the Mexican cactus pear in national and international markets is the innovation and creation of new high value-added products. This could be achieved by determining the nutritional and functional properties that differentiate the Mexican cactus pear from analogous products. In addition, providing functional prod ucts for a market in constant growth would offer a key competitive advantage and would allow the producers to diversify its commercialization, not as fresh fruit only, but also as an ingredient or high-value additive for the food industry. A commercialization of the cactus- pear based on its antioxidant properties could generate competitive advantages that may turn into business opportunities and the development of new products . Different studies with the varieties of European and Asian cactus pears have shown notable antioxidant activities that significantly reduce oxidative stress in patients and may help in preventing chronic pathologies (as diabetes and cancer) [85-87]. These pigments have shown beneficial effects on the redox-regulated pathways in volved in cell growth and inflammation, and have not shown toxic effects in humans [90,91]. In addition, a neuroprotector activity against oxidative damage induced in cultures of rat cortical cells has been attributed to the cactus pear flavonoids . Another beneficial effect of the fruit was observed in the prevention of stomach ulcers through the stimulation of prostaglandin production: cactus pear promoted mucous secretion of bicarbonate, involved in the protection of gastric mucosa . In the Institute of Health Sciences (Autonomous University of Hidalgo State) have been per formed studies to demostrate the chemopreventive capacity of the cactus pear. In this regard, the princkly pear variety red- purple showed an anticlastogenic effect directly proportional to the concentrations. The highest protection was obtained with the concentration of 25 mL/Kg (approximately, 80%) after 48 hours of treatment . The results indicated that the antiradical activities from yellow and white cactus pear cultivars were not significantly different and were lower than the average antiradical activities in red and purple cultivars. The red cactus pear from the state of Zaca tecas showed the highest antioxidant activity. The free radical scavenging activity for red cactus pears was significantly correlated to the concentration of total phenolic compounds (R2 = 0. All 18 cultivars of cactus pears studied showed sig 168 Oxidative Stress and Chronic Degenerative Diseases - A Role for Antioxidants nificant chelating activity of ferrous ions. Cranberries Among small soft-fleshed colorful fruits, berries make up the largest proportion consumed in our diet. The North American cranberry (Vaccinium macrocarpon) is of a growing public interest as a functional food because of potential health benefits linked to phytochemicals of the fruit. Cranberry juice has long been consumed for the prevention of urinary tract infec tions, and research linked this property to the ability of cranberry proanthocyanidins to in hibit the adhesion of Escherichia coli bacteria responsible for these infections . These studies, which brought to light the unique structural features of cranberry proanthocyani dins , have sparked numerous clinical studies probing a cranberrys role in the preven tion of urinary tract infections and targeted the nature of the active metabolites. Further antibacterial adhesion studies demonstrated that cranberry constituents also inhibit the ad hesion of Helicobacter pylori, a major cause of gastric cancer, to human gastric mucus . The earliest report of potential anti-carcinogenic activity appeared in 1996 in the University of Illinois . Subsequent studies with cranberry and other berries in cellular models have focused on some cancers such as breast, colon, liver, prostate and lung [100-102]. With respect to his genotoxic and/or antigenotoxic potential, there are few reports in the literature that demonstrate this effect and the majority of studies were per formed in vitro cell culture models [101,103,104]. During this period the body weight, the feed intake, and the determination of antigenotoxic potential were quantified. At the end of this period, we continued with the same determinations for one week more (recovery period) but any more administration of the substances. The animals treated with B[a]P showed a weight in crease after the first week of administration. In the second part of the assay, when the substances were not administered, these experimental groups re gained their normal weight. The same dose showed an anticytotoxic effect which corresponded to an improvement of 62. In the second period, all groups reached values that have been seen in the control group animals. Our results suggest that the inhibition of clastoge nicity of the cranberry ethanolic extract against B[a]P is related to the antioxidant capacity of the combination of phytochemicals present in its chemical composition . Grapefruit juice and naringin The grapefruit is a subtropical citrus tree known for its bitter fruit. His fruit (called toronja in Spanish) has become popular since the late 19th century, is yellow-orange skinned and largely an oblate spheroid and generally, is consumed in form of juice . The grapefruit juice is an excellent source of many nutrients and phytochemicals that con tribute to a healthy diet.
Probably mast cell-derived cytokines cheap sildenafil 25 mg visa, proteases and eicosanoids are also involved discount sildenafil 50 mg on-line. Blood basophils and eosinophils are also present in skin biopsy material from wheals of all ages and may also be a source of vasoactive mediators (Sabroe et al 100 mg sildenafil with mastercard. Clinical Features and Investigation Characteristically the wheals are intensely itchy, of less than 24 hours duration individu- ally and clear without marking the skin. Angioedema occurs in up to 50 per cent and af- fects skin and/or mucous membranes. Systemic symptoms are minimal in the majority but can be disabling for severely afected patients. Delayed pressure urticaria occurs concur- rently in up to 40 per cent of patients (Sabroe et al. When delayed pressure urti- caria is an accompanying feature, it is important to establish whether this physical urticaria or the accompanying spontaneous wheals and angioedema are the principal causes of the patients disability, since no further investigations are worth while for pure delayed pres- sure urticaria. The incidence of chronic spontaneous urticaria complicated by angioedema and delayed pressure urticaria, appears not so high in Japan and Asian countries according to the authors experiences (Tanaka et al. Chronic spontaneous urticaria may be a seriously disabling condition, causing occu- pational, social and personal disability of the same order as those consequent upon severe coronary artery disease (ODonnell et al. No laboratory investigations are normally indicated in the frst instance for anti-histamine responsive disease. Eforts should be directed at excluding urticarial vasculitis (by skin biopsy) and a diferential white blood cell count (for eosinophilia) in areas where parasite infestation is endemic. Checking thyroid function and autoantibodies can be rewarding to detect pa- tients with associated thyroid autoimmunity. In severely afected patients, poorly respon- sive to H1-antihistamines, referral to a specialised unit for investigation for autoimmune chronic urticaria should be considered (see below). Treatment General measures are important including a cool work and domestic environment, avoid- ance of alcohol indulgence, taking non-steroidal anti-infammatory drugs including aspi- rin, and wearing tight clothes. Although almost inevitably associated with modern living, stress, fatigue and intercurrent virus infections should at least be recognised by patients as the probable causes of occasional fare-ups of chronic urticaria. It is important to establish the diurnal periodicity of symptoms (itch occurs predominantly in the evening and at night) 10 in timing the dose. Up-dosing second generation antihistamines to four-fold above licence has been recommended for non-responders (Zuberbier, 2009) and this recommendation has been supported recently by well-conducted clinical studies for cold urticaria (Siebenhaar, 2009) and chronic spontaneous urticaria (Staevska, 2010). It has been proposed that H1-anti- histamines may exert an anti-allergic action independently of H1 receptors (Hayashi and Hashimoto, 1999). This consists of down-regulation of adhesion molecule expression lead- ing to reduced eosinophil and neutrophil migration and possibly a mast cell stabilising ef- fect. However, such actions of H1-antihistamines may occur only with regimens involving well above the licensed dosages. If a sedating H1 antihistamine is prescribed at night, it is important to draw the patients attention to the possibility of signifcant impairment of cognitive function the next morn- ing (Pirisi, 2000). Topical application of 1% menthol in aqueous cream may be appreciated by patients by providing rapid but temporary relief from pruritus. Cysteinyl leukotriene receptor antagonists may be efective in some patients especially those with delayed pressure urticaria. The efcacy of montelukast by itself or in combination with H1-antihistamine has been shown by controlled trials (Pacor, 2001; Erb- agci, 2002). Aggravation of urticaria by aspirin in combination with other leukotriene antagonists has been reported (Ohnishi-Inoue et al. Oral steroids in short tapering courses can be useful in emergencies when rapid control is necessary. However, they are not recommended as a routine treatment of chronic urti- caria, due to concern about side efects from long term administration (Fig. Tese patients are described as having autoimmune chronic urticaria (Grattan, 1991, Hide et al. Etiology The reason why these autoantibodies are present and causative in some patients with chronic urticaria and not others is unclear. Tere is also a positive association with other autoimmune dis- eases, notably autoimmune thyroid disease in patients with autoimmune urticaria (Leznof et al. Histamine release evoked by these antibodies from ba- sophil leucocytes of healthy donors can be inhibited by prior incubation with human re- combinant chain. How- ever, the binding of most of these types of autoantibodies are interfered with competitively by IgE to various degrees (Hide et al. Removal of IgE (by lactic acid stripping) en- ables the autoantibody to release histamine but reconstituting the IgE on the surface of the basophils inhibits release (Niimi et al. In about nine per cent of patients with chronic spontaneous urticaria, the IgG autoantibody reacts with the Fc portion of IgE itself. Studies looking at binding of monoclonal antibodies to the IgE heavy chain suggest that these functional anti-IgE au- toantibodies probably bind to the 4th constant domain (Grattan and Francis, 1999). The heat-resistance of histamine releas- ing activity in sera of patients with chronic urticaria has been also observed by other au- thors (Zweiman et al. The subclasses of IgG in autoimmune urticaria are predomi- nantly IgG1 and IgG3, which may readily activate complement (Fiebiger et al. Cause whealing in human skin following intradermal injection (see autologous serum skin test) (Sabroe et al. Removal by plasmapheresis results in remission of chronic urticaria in autoantibody positive patients (Grattan et al. Efectiveness of other immunomodulative therapies, such as ciclosporin and intravenous im- munoglobulin (Grattan et al. Removal of the antibodies by plasmapheresis leads to temporary remission of the urticaria (Grat- tan et al. The antibody also reproduces the urticarial wheal when introduced as an autologous serum injection into human skin, and causes histamine release from der- mal mast cells and blood basophils (Niimi et al. However, it should be noted that urticarial eruptions are not apparently observed even in the systemic anaphylac- tic reactions induced by antigen in animals, such as rodent and guinea-pigs. Increased histamine releasability from dermal mast cells and basophils is an important additional factor in the pathogenesis (Sabroe et al. This enhanced histamine releasability is possibly due to the action of cytokines or neuro- kines released locally. Tese cytokines also cause up-regulation of adhesion molecule ex- pression, leading to the substantial leucocyte infltrate characteristic of the histological ap- pearances of autoimmune urticaria. Alternatively, local cytokine and micro-circulatory diferences be- tween lung and skin may restrict access of the autoantibodies to tissue mast cells in the lungs. Tere is also functional heterogeneity between dermal and lung mast cells (Low- man et al. Greaves Clinical and Histological Features Detailed comparative reviews of the symptoms, clinical presentation and natural history of autoimmune and the other spontaneous chronic urticaria has failed to reveal diferences sufciently distinctive to be of diagnostic value (Sabroe et al. Patients with autoim- mune urticaria also tend to be less responsive to routine antihistamine treatment than other spontaneous, non-autoimmune urticaria patients. Again, the diference is not so conspicu- ous as to be useful as a discriminating marker for an autoimmune etiology on its own. This is not an original observation; Rorsman (1961) noted almost 45 years ago that chronic urticaria was associated with basopenia in some patients with chronic idiopathic (but not physical) urticaria. The fate of the cells is of interest; degranulation or destruction in the peripheral blood is an obvious possibility. Indeed, Kaplans group found the increase of basophils in skin of chronic idiopathic urti- caria with or without autoantibodies as well as T cells, eosinophils and neutrophils (Ying et al. The alternative of redistribution into the lesional skin of chronic urticaria may 10 account for the basopenia. Sabroe (1999b) carried out a detailed histological study of skin biopsy material from pa- tients with autoimmune and other spontaneous urticaria. More recently Kaplans group also found no diference in either the numbers of infammatory cells or the pattern of cytokine expressions between patients with and without autoantibody (Ying et al. Diagnosis As pointed out above, there are no clinical or histological features that can be used as a par- adigm in diagnosis (Sabroe et al. The autologous serum skin test is a useful screening procedure with a very high negative predictive value for functional autoantibodies (Konstantinou et al. This test is based upon the original fnding by Grattan (1986) that the serum of some patients with chronic idiopathic urticaria would cause a red wheal upon autologous injection into the patients uninvolved skin.
This sharing of the receptor subunits among different cytokines may partially explain some of the func- tional redundancy and costimulation of their production and activity sildenafil 25mg visa. Most cytokine receptors are members of the cytokine receptor superfamily which is characterized by a conserved amino acid motif in the extracellular portion and in a region proximal to the membrane (9 buy sildenafil 50 mg on line, 10) discount sildenafil 50mg amex. This superfamily can be divided into three subfamilies according to a shared subunit, i. The receptors in the chain subfamily consist of three subunits (,, ): the, and subunits are members of the superfamily and are constitutively expressed on T-cells. Receptors in this subfamily have two subunits, with the chain distinct for each receptor. Both the and chains are members of the cytokine receptor superfamily, and signaling is mediated through lig- and interactions of the cytoplasmic regions on the shared chain. Formation of homodimers and heterodimers with gp 130 mediates signal transduction by these receptors. This dimerization (or oligomerization in cytokine receptors with more than two chains) increases the affinity of the dimers cytoplasmic domain that is proximal to the membrane to bind two Jaks. Both the Jaks and the cytoplasmic region of the receptor chain become phosphorylated simultaneously. This phosphorylation subsequently becomes a catalyst for the binding and phosphoryla- tion of two latent cytoplasmic transcription factors called Stats, i. The actual number of Stats is uncertain, but at least six have been characterized. Given the number of Jaks and Stats, it is understandable that different cytokine recep- tors associate with different Jaks, which then catalyze the binding and phosphorylation of different Stats (16). To add to the complexity, Stats can be phosphorylated by kinases other than Jaks, e. They share a high basic nature and can bind heparin through heparin binding domains. Chemokines are produced by nearly every cell type in response to inflammatory sig- nals, particularly signals that activate interactions between leukocytes and endothelial cells. Chemokines range between 68 to 100 amino acids in length and are defined by conserved motifs containing either two or four cysteine residues that form disulfide bonds in the protein tertiary structure. Genes encoding members of each group appear to cluster on the same chromosomes, i. The responsiveness to chemokine stimulation depends not only on the specific type of leukocytes but also on the condi- tions of stimulation, e. Data suggest that chemokines have a role in sev- eral other processes, including angiogenesis, tissue development, and fibrosis. Chemokine Receptors Chemokines bind to a distinct class of receptors whose structure is similar to that of rhodopsin. The receptor polypeptide has seven hydrophobic domains passing through the membrane as -helices with an extracellular aminoterminus and an intracellular carboxy terminus (21). Receptor binding can be restricted to a specific chemokine or shared among several chemokines, e. Humans have one chemokine receptor that is promiscuous since it binds to numer- ous chemokines. This receptor, the Duffy blood group antigen, was first identified on red blood cells but is also expressed by several nonerythroid cells, e. Interestingly, the Duffy antigen is a factor in infections with Plasmodium vivax in which the parasite utilizes this receptor to invade erythrocytes (22). In people of African descent, this receptor may not be expressed on red blood cells, and they are resistant to infections with P. The mechanism by which expression of a chemokine receptor is advantageous to the virus is not clear (21). The signaling of cellular response to chemokines occurs through G proteins (gua- nine nucleotide binding regulatory proteins) coupling to initiate phosphoinositide 2 hydrolysis. The resultant increase in diacylglycerol and cytosolic Ca leads to activa- tion of protein kinase C (25). Despite the complex- ity of cytokine activity, it is important to appreciate the role of the interplay of the cytokines with their various target cells in the immune response to an inflammatory agent. The immune response during the early stages will either eradicate the infectious agent or set the stage for the type of chronic immune response. When the control mech- anism for the type of cytokine response is dysfunctional, the result may be the devel- opment of a chronic or progressive infection rather than eradication or containment of the infectious agent, e. The hosts genetic background is also a factor in the development of chronic inflammatory response and pathology. Autoimmune diseases result from perturbation of the immune system either intrinsically for unknown rea- sons, (e. The purpose of this section is to provide a background sketch of the role of the cytokine network in the responses of the immune system to an infectious agent prior to its commitment to the appropriate immune protective mechanism, i. Initial Inflammatory Response and Leukocyte Migration The bodys innate immune response to an invading organism results in the recruitment of leukocytes and phagocytosis of the organism. Numerous factors, including bacterial components, will stimulate migration of the leukocytes. Immunotherapies that are intended to interfere with the Cytokines, Cytokine Antagonists, and Growth Factors 125 activity of these cytokines and other inflammatory molecules, e. These cytokines in turn stimulate their target cells to produce a number of different mole- cules. These latter molecules are important in the recruit- ment of leukocytes from the circulation to the infected tissue. With expression of leukocyte adhesion molecules, the leukocytes loosely attach to the endothelial cells through the oligosaccharides on their membranes. With their movement slowed by this loose attachment, the leukocytes will begin to roll along the endothelial surface. The chemokines released from macrophages, the surrounding tissue cells, and the endothelial cells in response to the bacterial components bind to the endothelium, where they cause the rolling leukocytes to adhere more firmly to the endothelium through binding of the integrins to their ligand. The leukocytes then migrate through the endothelium and move up a gradient of chemokine concentrations to the inflammatory site. The types of leukocytes recruited to the inflammatory site can differ depending on the source of inflammation, (e. Activation of T-Helper Cells: Th1/Th2 Subsets When stimulated, T-cells produce different types and amounts of cytokines, which in turn, characterizes the functional response of the T-cells. The cytokines produced by each subset regulates the function and devel- opment of the other. Several immunotherapies for infectious diseases have focused on the manipulation of the type or degree of T-cell response, e. Although this response is intended to eradicate intracellular pathogens, it may also be associated with autoimmune diseases. Th2 cytokines activate mast cells, eosinophils, and elevation in IgE levels and are associated with the immune response to allergens and helminths. Chemokines have a role in lymphocyte response to infections with the orchestration of the movement of the right lymphocyte, i. The T-helper cell subsets tend to colocalize with different leukocytes (although not always). The Th1 subset of cells tends to colocalize with macrophages and neutrophils, whereas Th2 are more often associated with eosinophils and basophils. Much of the data on chemokine receptor expres- sion analysis in T-helper subsets are from in vitro experiments, and further studies are needed to improve our comprehension of the role of chemokines in lymphocyte migration. Since the elucidation of the Th1/Th2 subsets of helper T-cells, their function has probably been oversimplified in the assignment of a Th1 response to intracellular pathogens and a Th2 response to extracellular organisms. However, for many infectious Cytokines, Cytokine Antagonists, and Growth Factors 127 diseases a response by Th1 and Th2 cells at different time points is needed to control or eradicate the infection. In addition, unlike in the mouse, some cytokines are syn- thesized by both T-cell subsets in humans. This coproduction for some cytokines and the redundancy in the activity of the cytokine network suggest that the immune response to different pathogens represents a weighted response involving both T-cell subsets rather than one limited solely to either Th1 or Th2. Therefore, it is important to rec- ognize that the therapeutic effect of an immunotherapy intended to manipulate the effect of one cytokine will result not only from the modulation of that cytokine but also the effect that that modulation has on other cytokines in the network. Modulation of host defenses by cytokines: evolving adjuncts in pre- vention and treatment of serious infections in immunocompromised hosts. Regulation of immunoglobulin production in hyperim- munoglobulin E recurrent-infection syndrome by interferon-gamma. Airway epithelial cell expression of interleukin-6 in transgenic mice: uncoupling airway inflammation and bronchial hyperreactivity.
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