Protective Mode Of Action Research Articles

Growth behavior of wood-destroying fungi in chemically modified wood: wood degradation and translocation of nitrogen compounds

Abstract Chemical wood modification has been used to modify wood and improve its decay resistance. However, the mode of protective action is still not fully understood. Occasionally, outdoor products made from chemically modified timber (CMT) show internal decay while their outer shell remains intact. Hence, it was hypothesized that wood decay fungi may grow through CMT without losing their capability to degrade non-modified wood. This study aimed at developing a laboratory test set-up to investigate (1) whether decay fungi grow through CMT and (2) retain their ability to degrade non-modified wood. Acetylated and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) treated wood were used in decay tests with modified ‘mantle specimens’ and untreated ‘core dowels’. It became evident that white rot (Trametes versicolor), brown rot (Coniophora puteana) and soft rot fungi can grow through CMT without losing their ability to degrade untreated wood. Consequently, full volume impregnation of wood with the modifying agent is required to achieve complete protection of wooden products. In decay tests with DMDHEU treated specimens, significant amounts of apparently non-fixated DMDHEU were translocated from modified mantle specimens to untreated wood cores. A diffusion-driven transport of nitrogen and DMDHEU seemed to be responsible for mass translocation during decay testing.

Baicalin reversal of DNA hypermethylation-associated Klotho suppression ameliorates renal injury in type 1 diabetic mouse model

ABSTRACT Baicalin is a flavone glycoside that possesses numerous pharmacological properties. but its protective mode of action in kidney injury induced by diabetes mellitus remains incompletely understood. Using a streptozotocin (STZ)-induced diabetic mouse model, we found that baicalin could ameliorate diabetes-induced the pathological changes of the kidney function and morphology through suppressing inflammation and oxidative stress. Furthermore, baicalin treatment could alleviate interstitial fibrosis in the diabetic kidney via inhibiting epithelial-to-mesenchymal transition (EMT), which was accompanied by a sharp upregulation of Klotho, the endogenous inhibitor of renal fibrosis. We further verified that baicalin-rescued expression of Klotho was associated with Klotho promoter hypomethylation due to aberrant methyltransferase 3a expressions. Klotho knockdown via RNA interferences largely abrogated the anti-renal fibrotic effects of Baicalin in HK2 cells. These findings suggested that baicalin could alleviate renal injury-induced by diabates through partly modulating Klotho promoter methylation, which provides new insights into the treatment of diabetic nephropathy.

Determination of antioxidant potential of Salix aegyptiaca L. through biochemical analysis

Salix aegyptiaca L., commonly called musk willow, is a medicinal herb in use since ancient time. However, information on its mode of protective action is scanty. Considering its significance and wide applications, here, we explored the same using its hydroethanolic bark extract. The results of nitric oxide assay indicated the free radical scavenging ability of the bark extract. In the ex vivo study, the extract of bark was found to exert protective effects against protein and membrane damage caused by the Fenton’s reagent in the liver homogenate of C57BL/6 mice. In in vivo studies, the specific activities of enzymes involved in antioxidant function and the level of reduced glutathione (GSH) enhanced in the liver of six weeks old C57BL/6 mice treated with extract of bark. On the other hand, the oxidative damage in the liver determined in terms of TBARS was decreased significantly. The concomitant increase in the free radical metabolizing enzymes and the content of GSH; and inhibition of oxidative damage is suggestive of possibility of enhanced antioxidant potential of animals. The bark extract also enhanced the specific activities of phase I and phase II enzymes, which would likely to contribute in the detoxification. In conclusion, the S. aegyptiaca scavenges the free radicals, elevates the endogenous antioxidant status and detoxifies the toxic agents which determine its beneficial effects.

Human mesenchymal stromal cells inhibit platelet activation and aggregation involving CD73-converted adenosine

BackgroundMesenchymal stromal cells (MSCs) are promising cell therapy candidates. Clinical application is considered safe. However, minor side effects have included thromboembolism and instant blood-mediated inflammatory reactions suggesting an effect of MSC infusion on hemostasis. Previous studies focusing on plasmatic coagulation as a secondary hemostasis step detected both procoagulatory and anticoagulatory activities of MSCs. We now focus on primary hemostasis and analyzed whether MSCs can promote or inhibit platelet activation.MethodsEffects of MSCs and MSC supernatant on platelet activation and function were studied using flow cytometry and further platelet function analyses. MSCs from bone marrow (BM), lipoaspirate (LA) and cord blood (CB) were compared to human umbilical vein endothelial cells or HeLa tumor cells as inhibitory or activating cells, respectively.ResultsBM-MSCs and LA-MSCs inhibited activation and aggregation of stimulated platelets independent of the agonist used. This inhibitory effect was confirmed in diagnostic point-of-care platelet function analyses in platelet-rich plasma and whole blood. Using inhibitors of the CD39–CD73–adenosine axis, we showed that adenosine produced by CD73 ectonucleotidase activity was largely responsible for the LA-MSC and BM-MSC platelet inhibitory action. With CB-MSCs, batch-dependent responses were obvious, with some batches exerting inhibition and others lacking this effect.ConclusionsStudies focusing on plasmatic coagulation suggested both procoagulatory and anticoagulatory activities of MSCs. We now show that MSCs can, dependent on their tissue origin, inhibit platelet activation involving adenosine converted from adenosine monophosphate by CD73 ectonucleotidase activity. These data may have strong implications for safety and risk/benefit assessment regarding MSCs from different tissue sources and may help to explain the tissue protective mode of action of MSCs. The adenosinergic pathway emerges as a key mechanism by which MSCs exert hemostatic and immunomodulatory functions.

Combination of engineered neural cell adhesion molecules and GDF-5 for improved neurite extension in nerve guide concepts

Current therapeutical approaches for the treatment of severe lesions in the peripheral nervous system rely on the use of autologous tissue or the body's own Schwann cells. However, these approaches are limited and alternative strategies for peripheral nerve regeneration are required. Here we evaluate combinations of a variety of neuronal regeneration factors including engineered cell adhesion molecules and growth factors in embryonic model neurons to test the possible improvement of artificial nerve guides by cooperative mechanisms. Cell adhesion molecules L1 and neurofascin synergistically promote neurite elongation. The outgrowth promoting properties of both proteins can be combined and further increased within one chimeric protein. Addition of growth and differentiation factor 5 (GDF-5) further enhances neurite outgrowth in a substrate-independent manner. This effect is not due to a protective mode of action of GDF-5 against pro-apoptotic stimuli. Consequently, the study supports the idea that different modes of action of pro-regenerative factors may contribute synergistically to neurite outgrowth and emphasizes the applicability of combinations of proteins specifically involved in development of the nervous system for therapeutical approaches.

Weak inhibitors protect cholinesterases from strong inhibitors (paraoxon): in vitro effect of ranitidine

Metoclopramide (MCP) is a dopamine receptor antagonist and serotonin receptor agonist widely used as an antiemetic and gastric prokinetic drug. In addition MCP is a weak and reversible inhibitor of cholinesterases. We have shown that MCP has a cholinesterase protective effect against inhibition by organophosphates. The putative mode of protective action of MCP is competition for the active site of the enzyme with the more potent organophosphate. In the present paper we present our results using another weak inhibitor of cholinesterases: ranitidine (RAN). The purpose of the study was to quantify in vitro the extent of RAN-conferred protection, using paraoxon (POX) as an inhibitor. Paraoxon is a non-neuropathic organophosphate responsible for a large number of accidental or suicidal exposures. Red blood cell (RBC) acetylcholinesterase (AChE) activities in whole blood and butyrylcholinesterase (BChE) activities in human plasma were measured photometrically in the presence of different POX and RAN concentrations and the IC50 was calculated. Determinations were repeated in the presence of increasing RAN concentrations. The IC50 shift induced by the presence of RAN increases with the RAN concentration in a linear manner. The shift was more pronounced with RBC-AChE. The protective effect of RAN on cholinesterase could be of practical relevance in the treatment of POX poisoning. We conclude that in vivo testing of RAN as an organophosphate protective agent is warranted.

Protection against cocaine and combined cocaine-ethanol toxicities in mice by imidazobenzodiazepine Ro 15-4513

The effects of Ro 15-4513 in preventing cocaine and combined cocaine-ethanol toxicities were examined in mice. Ro 15-4513 is a partial inverse agonist of benzodiazepine receptors, which has been implicated in ethanol lethality and cocaine-induced seizures. Ro 15-4513 (5 mg/kg, 10 mg/kg, or 15 mg/kg) was administered intraperitoneally 10 min before the administration of saline and cocaine (75 mg/kg) in the cocaine groups, or before ethanol (3 g/kg) and cocaine (75 mg/kg) in the cocaine-ethanol groups. In both cocaine and cocaine-ethanol groups, two distinct groups of dead animals meeting the same criteria, the IL (immediate lethal) and DL (delayed lethal) groups, could be differentiated, depending on their survival times, observed disorders, and drug levels at the time of death. Differences in the seizure scores further subdivided the two groups. Ro 15-4513 protected mainly against the immediate lethality in the cocaine groups and mainly against the delayed lethality in the cocaine-ethanol groups. The dose of Ro 15-4513 providing the maximal protection against the lethal effects of these drugs was 10 mg/kg in the cocaine groups, and 5 mg/kg in the cocaine-ethanol groups. The sum of the lethalities was still higher with the maximal effective dose of Ro 15-4513 in the cocaine-ethanol groups than in the cocaine groups. In the cocaine-ethanol groups, 5 mg/kg of Ro 15-4513 attenuated both brain and liver cocaethylene levels. Cocaine-induced seizures were also attenuated by any dose of Ro 15-4513 used in the cocaine groups. Although some discrepancies were observed in the protective properties, some validity for the use of Ro 15-4513, a drug with more than one mode of protective action, was demonstrated in this study.

Protective mechanisms of dietary fibers in nutritional carcinogenesis.

Fibers in foods are complex carbohydrates. There are several types of fiber, but, for the purpose of mechanistic insight into their mode of protective action in carcinogenesis, classification into two broad types, soluble and insoluble fibers, is warranted. Soluble fibers are present in fruits, vegetables, and certain grains like oats. This type of fiber undergoes metabolism in the small intestine and especially in the large intestine through bacterial enzymes, converting it to products that increase stool size only moderately. But, they have appreciable effects in modifying the metabolism of colon carcinogens like azoxymethane to yield detoxified products and, thus, reducing colon carcinogenesis. In contrast, insoluble fibers present in sizeable amounts in bran cereals, like wheat or rice, are not significantly metabolized by enzymes in the intestinal flora. Such fibers increase stool size substantially through several mechanisms, including higher water retention. The larger bulk dilutes carcinogens, especially tumor promoters such as secondary bile acids, resulting in lower risk of colon cancer in animals and in humans. Evidence in animal models and in humans also indicates that fiber may lower the risk of breast cancer, possibly via an endocrine mechanism. Based on these concepts, increased intake of total fiber, but especially of wheat bran cereal fiber, to yield a daily stool in adults of about 200 grams can significantly reduce the risk of colon cancer and, to a lesser but definite extent, of breast cancer. Thus, adequate fiber intake from cereals, fruits, and vegetables can help prevent important types of human cancer.

Effects of calcium, calcium entry blockers and calmodulin inhibitors on atrioventricular conduction disturbances induced by hypoxia.

Effects of hypoxia on atrioventricular conduction were investigated in the Langendorff-perfused isolated heart of the rabbit with various extracellular calcium concentrations ([Ca2+]) as well as in the presence of verapamil, nifedipine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7) and chlorpromazine. The prolongation of the atrio-His (AH) interval by hypoxia for 7 min was greater with increasing [Ca2+]o ranging from 1.2 to 5.2 mM. At [Ca2+]o of over 3.2 mM under hypoxic conditions, AH block of the Wenckebach type was observed in some cases. Verapamil (5 X 10(-8) M) and nifedipine (5 X 10(-8) M) caused a significant prolongation of AH intervals before hypoxia. However, the intensity of AH prolongation due to hypoxia was significantly attenuated in the presence of the calcium entry blocker, and AH block was not induced even at 3.2 mM [Ca2+]o. W-7 (5 X 10(-6) M) and chlorpromazine (10(-6) M) did not affect the AH intervals before hypoxia. The hypoxia-induced prolongation of the AH interval or AH block was prevented in the presence of these drugs. W-5, a chlorine-deficient derivative of W-7, showed no protection against hypoxia-induced AV nodal conduction disturbances. These findings suggest that hypoxia-induced AV nodal conduction disturbance is explained, at least in part, by the electrical uncoupling of nodal cells, probably due to the calcium overload. This conduction disturbance is protected by calcium entry blockers or by calmodulin inhibitors, but the mode of protective action is not the same for these different categories of drugs.

Inhibition of cutinase and prevention of fungal penetration into plants by benomyl—A possible protective mode of action

Cutinase purified from Fusarium solani f. sp. pisi was effectively inhibited by the fungicide benomyl. This irreversible inhibition was shown to be caused by the reaction of n-butylisocyanate, a breakdown product of benomyl, with the active serine in the enzyme. Methyl-2-benzimidazolecarbamate (MBC), the other breakdown product of benomyl, had no cutinase inhibitory activity. The fungicidal action of benomyl was measured by a bioassay using pea stems with or without intact cuticular and cell wall barriers. Benomyl prevented infection of Pisum sativum by conidia of F. solani f. sp. pisi only on intact pea stems with 50% efficiency at 7 μ M, but was without effect on wounded stems or when benomyl (up to 50 μ M) was applied 24 hr after inoculation with spores. Both MBC and benomyl strongly inhibited mycelial growth with 50% inhibition at 2 μ M indicating a toxic mode of action. The prevention of fungal infection on only intact stem surfaces was established, however, with a fungal strain which was relatively tolerant to the toxic effect of these fungicides. With this strain complete protection was obtained at 5 μ M benomyl which caused only 30% inhibition of growth. These results suggest that benomyl at low concentrations prevented fungal penetration and thus infection probably through inhibition of cutinase. It is also shown that treatment of cutin with n-butylisocyanate made it resistant to cutinase action.