N-acetylcysteine protects epithelial cells against the oxidative imbalance due to Clostridium difficile toxins

Androcin 18-1, a novel scorpion-venom peptide, shows a potent antitumor activity against human U87 cells via inducing mitochondrial dysfunction

Scorpion venom is a potent natural source for antitumor drug development due to the multiple action modes of anticancer components. Although the sequence of Androcin 18-1 has been identified from the transcriptome profile of the scorpion venom Androctonus bicolor, its bioactivity remains unclear. In this study, we described the antitumor mechanism whereby Androcin 18-1 inhibits the proliferation and induces apoptosis by inducing cell membrane disruption, ROS accumulation, and mitochondrial dysfunction in human U87 glioblastoma cells. Moreover, Androcin 18-1 could suppress cell migration via the mechanisms associated with cytoskeleton disorganization and MMPs/TIMPs expression regulation. The discovery of this work highlights the potential application of Androcin 18-1 in drug development for glioblastoma treatment.

Dietary pattern in autism increases the need for probiotic supplementation: A comprehensive narrative and systematic review on oxidative stress hypothesis

Autism spectrum disorders (ASDs) are associated with specific dietary habits, including limited food selection and gastrointestinal problems, resulting in an altered gut microbiota. Autistic patients have an elevated abundance of certain gut bacteria associated with increased oxidative stress in the gastrointestinal tract. Probiotic supplementation has been shown to decrease oxidative stress in a simulated gut model, but the antioxidant effects of probiotics on the oxidative stress of the gut in autistic patients have not been directly studied. However, it is speculated that probiotic supplementation may help decrease oxidative stress in the gastrointestinal tract of autistic patients due to their specific dietary habits altering the microbiota. PubMed, Scopus and Web of Science databases and Google Scholar were searched up to May 2023. This systematic-narrative review aims to present the latest evidence regarding the changes in eating habits of autistic children which may further increase the gut microbiota induced oxidative stress. Additionally, this review will assess the available literature on the effects of probiotic supplementation on oxidative stress parameters.

Double-blind, Randomized, Placebo-controlled Trial With N-acetylcysteine for Treatment of Severe Acute Respiratory Syndrome Caused by Coronavirus Disease 2019 (COVID-19)

Background

A local increase in angiotensin 2 after inactivation of angiotensin-converting enzyme 2 by SARS-CoV-2 may induce a redox imbalance in alveolar epithelium cells, causing apoptosis, increased inflammation and, consequently, impaired gas exchange. We hypothesized that N-acetylcysteine (NAC) administration could restore this redox homeostasis and suppress unfavorable evolution in Covid-19 patients.

Objective

To determine whether NAC in high doses can avoid respiratory failure in patients with Covid-19.

Methods

It was a double-blind, randomized, placebo-controlled, unicentric trial, conducted at the Emergency Department of Hospital das Clínicas, São Paulo, Brazil. We enrolled 135 patients with severe Covid-19 (confirmed or suspected), with an oxyhemoglobin saturation of less than 94% or respiratory rate higher than 24 breaths/min. Patients were randomized to receive NAC 21 g (approximately 300 mg/kg) for 20 hours, or dextrose 5%. Primary endpoint was the need for mechanical ventilation. Secondary endpoints were time of mechanical ventilation, admission to ICU, time in ICU, and mortality.

Results

Baseline characteristics were very similar in the two groups, with no significant difference in age, sex, comorbidities, medicines taken, and disease severity. Also, groups were similar in laboratory tests and chest CT scan findings. Sixteen patients (23.9%) in the Placebo group were submitted to endotracheal intubation and mechanical ventilation, compared to 14 patients (20.6%) in the NAC group (p=0.675). No difference was observed in secondary endpoints.

Conclusion

Administration of NAC in high doses did not affect the evolution of severe Covid-19.

Investigation of genetic toxicity and oxidative stress of Clostridium perfringens epsilon toxin type D on human peripheral blood lymphocytes

Epsilon toxin (Etx) is an enormously potent pore-forming toxin and a category B biological agent. Etx is the main virulence determinant of Clostridiumperfringens types B and D toxin. It has a cytotoxic effect on distal and collecting kidney tubules. Also, Etx crosses the blood-brain barrier, binds to myelin structures, and destroys oligodendrocytes. The main purpose of this study was to investigate the toxic effects of Etx on human blood lymphocytes, which we examined for the first time for the genetic toxicity of this bacterial toxin. In this study, after taking blood and dividing into nine groups and putting in contact with different dilutions of Etx (1,5,10,25,50,100 and 200 μM), methotrexate (750 μM), and normal saline by Cytokinesis blocked micronucleus (CBMN) assay, we looked at genetic toxicity and the level of oxidative stress created in the under study lymphocytes. The results of this study showed that Etx has significant oxidative stress effects on human lymphocytes at doses above 25 μM, and also this bacterial toxin significantly increases the number of micronuclei formed in lymphocytes. The results of this study indicate that Etx has toxic effects it is genetic and interferes with cell division processes. Thus, human lymphocytes can be used extensively in future studies on Etx.

Clostridium difficile toxin B-induced necrosis is mediated by the host epithelial cell NADPH oxidase complex

Clostridium difficile infection (CDI) is a leading cause of health care-associated diarrhea and has increased in incidence and severity over the last decade. Pathogenesis is mediated by two toxins, TcdA and TcdB, which cause fluid secretion, inflammation, and necrosis of the colonic mucosa. TcdB is a potent cytotoxin capable of inducing enzyme-independent necrosis in both cells and tissue. In this study, we show that TcdB-induced cell death depends on assembly of the host epithelial cell NADPH oxidase (NOX) complex and the production of reactive oxygen species (ROS). Treating cells with siRNAs directed against key components of the NOX complex, chemical inhibitors of NOX function, or molecules that scavenge superoxide or ROS confers protection against toxin challenge. To test the hypothesis that chemical inhibition of TcdB-induced cytotoxicity can protect against TcdB-induced tissue damage, we treated colonic explants with diphenyleneiodonium (DPI), a flavoenzyme inhibitor, or N-acetylcysteine (NAC), an antioxidant. TcdB-induced ROS production in colonic tissue was inhibited with DPI, and both DPI and NAC conferred protection against TcdB-induced tissue damage. The efficacy of DPI and NAC provides proof of concept that chemical attenuation of ROS could serve as a viable strategy for protecting the colonic mucosa of patients with CDI.

Vanadium inhalation induces actin changes in mice testicular cells

Infertility is becoming a health problem, which has increased mainly in megacities, and several studies have shown its association with environmental pollution. Air pollution has been linked to alterations in sperm parameters, both in humans and animal models. In male humans, it has been associated with reduced semen quality and DNA alterations. Vanadium is a transition element that has increased in recent decades as a component of air suspended matter and has been associated with reprotoxic effects in animal models. Few are the mechanisms described by which the vanadium produces these effects, and cytoskeleton interaction is a possibility. We reported immunohistochemical changes in actin testicular cytoskeleton in a vanadium inhalation experimental mice model. Our findings show that exposure to vanadium pentoxide (0.02 M) results in actin decrease in testicular cells from 3-12 weeks exposure time; this effect was statistically significant and exposure time dependent. Actin cytoskeleton damage is a mechanism that could explain vanadium reprotoxic effects and its association with impaired fertility.

The interactive effects of cytoskeleton disruption and mitochondria dysfunction lead to reproductive toxicity induced by microcystin-LR

The worldwide occurrence of cyanobacterial blooms evokes profound concerns. The presence of microcystins (MCs) in waters and aquatic food increases the risk to human health. Some recent studies have suggested that the gonad is the second most important target organ of MCs, however, the potential toxicity mechanisms are still unclear. For a better understanding of reproductive toxicity of MCs on animals, we conducted the present experimental investigation. Male rats were intraperitoneally injected with MC-LR for 50 d with the doses of 1 and 10 µg/kg body weight per day. After prolonged exposure to MC-LR, the testes index significantly decreased in 10 µg/kg group. Light microscope observation indicated that the space between the seminiferous tubules was increased. Ultrastructural observation showed some histopathological characteristics, including cytoplasmic shrinkage, cell membrane blebbing, swollen mitochondria and deformed nucleus. Using Q-PCR methods, the transcriptional levels of some cytoskeletal and mitochondrial genes were determined. MC-LR exposure affected the homeostasis of the expression of cytoskeletal genes, causing possible dysfunction of cytoskeleton assembly. In MC-LR treatments, all the 8 mitochondrial genes related with oxidative phosphorylation (OXPHOS) significantly increased. The reactive oxygen species (ROS) level significantly increased in 10 µg/kg group. The mitochondria swelling and DNA damage were also determined in 10 µg/kg group. Hormone levels of testis significantly changed. The present study verified that both cytoskeleton disruption possibly due to cytoskeletal reorganization or depolymerization and mitochondria dysfunction interact with each other through inducing of reactive oxygen species and oxidative phosphorylation, and jointly result in testis impairment after exposure to MC-LR.

Diverse protective roles of the actin cytoskeleton during oxidative stress

Actin oxidation is known to result in changes in cytoskeleton organization and dynamics. Actin oxidation is clinically relevant since it occurs in the erythrocytes of sickle cell patients and may be the direct cause of the lack of morphological plasticity observed in irreversibly sickled red blood cells (ISCs). During episodes of crisis, ISCs accumulate C284-C373 intramolecularly disulfide bonded actin, which reduces actin filament dynamics. Actin cysteines 284 and 373 (285 and 374 in yeast) are conserved, suggesting that they play an important functional role. We have been investigating the physiological roles of these cysteines using the model eukaryote Saccharomyces cerevisiae in response to oxidative stress load. During acute oxidative stress, all of the F-actin in wild-type cells collapses into a few puncta that we call oxidation-induced actin bodies (OABs). In contrast, during acute oxidative stress the actin cytoskeleton in Cys-to-Ala actin mutants remains polarized longer, OABs are slower to form, and the cells recover more slowly than wild-type cells, suggesting that the OABs play a protective role. Live cell imaging revealed that OABs are large, immobile structures that contain actin-binding proteins and that can form by the fusion of actin cortical patches. We propose that actin's C285 and C374 may help to protect the cell from oxidative stress arising from normal oxidative metabolism and contribute to the cell's general adaptive response to oxidative stress.

Yeast, beef and pork extracts counteract Clostridium difficile toxin A enterotoxicity

Clostridium difficile is responsible for a large proportion of nosocomial cases of antibiotic-associated diarrhoea and pseudomembranous colitis. The present study provides evidence that yeast, beef and pork extracts, ingredients commonly used to grow bacteria, can counteract C. difficile toxin A enterotoxicity in vitro and in vivo. In model intestinal epithelial cells the individual extracts could prevent the toxin A-induced decrease in epithelial barrier function and partially prevented actin disaggregation and cell rounding. Mice with ad libitum access to individual extracts for 1 week had almost complete reduction in toxin A-induced fluid secretion in intestinal loops. Concomitantly, the toxin A-induced expression of the essential proinflammatory mediator Cox-2 was normalized. Moreover this protective effect was also seen when mice received only two doses of extract by intragastric gavage within 1 week. These results show that yeast, beef and pork extracts have the potential to counteract the intestinal pathogenesis triggered by C. difficile toxin A.

Effects of acetylcysteine and migration of resident eosinophils in an in vitro model of mucosal injury and restitution in equine right dorsal colon

OBJECTIVES

To evaluate the in vitro protective effects of acetylcysteine and response of resident mucosal eosinophils in oxidant-induced injury to tissues of right dorsal colon of horses.

ANIMALS

9 adult horses.

PROCEDURE

Gastrointestinal mucosa was damaged in vitro with 3 mM hypochlorous acid (HOCl), with and without prior exposure to 6mM acetylcysteine. Control tissues were not exposed to HOCl or acetylcysteine. Control and damaged tissues were incubated in Krebs-Ringer-bicarbonate solution and tissue resistance measured during 240 minutes. Tissue permeability to radiolabeled mannitol was also used to assess mucosal barrier integrity. Tissues were examined by light microscopy before and after HOCl exposure and during and after incubation.

RESULTS

Exposure to HOCl caused tissue damage and decreased tissue resistance. Restitution did occur during the incubation period. Eosinophils were located near the muscularis mucosae in freshly harvested tissues and migrated towards the luminal surface in response to HOCl-induced injury. Compared with tissues treated with HOCl without acetylcysteine, pretreatment with acetylcysteine prevented HOCl-induced tissue damage, changes in resistance, and histologically detectable eosinophil migration. The permeability to mannitol increased to the same extent in tissues treated with HOCl alone or with acetylcysteine and HOCl.

CONCLUSIONS AND CLINICAL RELEVANCE

Eosinophils migrated toward the mucosal surface in equine colon in response to oxidant-induced damage in vitro. This novel finding could be relevant to inflammation in equine colon and a pathophysiologic feature of many colonic diseases. Acetylcysteine protected the mucosa against oxidant-induced injury and may be useful as a treatment option for various gastrointestinal tract disorders in horses.

Influence of thiol balance on micellar cholesterol handling by polarized Caco-2 intestinal cells

The in vitro thiol redox modulation of cholesterol homeostasis was investigated in polarized Caco-2 intestinal cells. Cells were pre-incubated with the pro-oxidant compound CuSO4 or with the antioxidant N-acetylcysteine (NAC), to induce a mild shift of the intracellular redox potential toward, respectively, a more oxidizing or a more reducing equilibrium, via a manipulation of intracellular soluble thiols (glutathione). Then, monolayers were exposed to micellar cholesterol and both the cholesterol uptake and export, as well as the cholesteryl ester cycle, were analyzed. We found that pro-oxidizing conditions induced a significant cholesterol retention within the cells, particularly in the unesterified form (FC), as a result of an augmented sterol incorporation coupled with a reduced rate of FC esterification. A reduction in FC export was also evident. Furthermore, the combination of FC retention and the oxidative imbalance leads to significant alterations of the monolayer integrity, evidenced by both the enhanced tight junction permeability and the lactate dehydrogenase release into the basolateral medium. In contrast, a more reducing environment generated by NAC pre-treatment favors the limitation of the resident time of FC into the cells, via a reduced cholesterol uptake and a concomitant increased cholesterol esterification. In addition, a significant higher FC extrusion into the basolateral medium was also appreciable. Our results indicate that the thiol balance of intestinal cells may be critical for the regulation of cholesterol homeostasis at the intestinal level, influencing the lipid transport throughout the intestinal barrier.

Induction of glia maturation factor-beta in proximal tubular cells leads to vulnerability to oxidative injury through the p38 pathway and changes in antioxidant enzyme activities

Proteinuria is an independent risk factor for progression of renal diseases. Glia maturation factor-beta (GMF-beta), a 17-kDa brain-specific protein originally purified as a neurotrophic factor from brain, was induced in renal proximal tubular (PT) cells by proteinuria. To examine the role of GMF-beta in PT cells, we constructed PT cell lines continuously expressing GMF-beta. The PT cells overexpressing GMF-beta acquired susceptibility to cell death upon stimulation with tumor necrosis factor-alpha and angiotensin II, both of which are reported to cause oxidative stress. GMF-beta overexpression also promoted oxidative insults by H2O2, leading to the reorganization of F-actin as well as apoptosis in non-brain cells (not only PT cells, but also NIH 3T3 cells). The measurement of intracellular reactive oxygen species in the GMF-beta-overexpressing cells showed a sustained increase in H2O2 in response to tumor necrosis factor-alpha, angiotensin II, and H2O2 stimuli. The sustained increase in H2O2 was caused by an increase in the activity of the H2O2-producing enzyme copper/zinc-superoxide dismutase, a decrease in the activities of the H2O2-reducing enzymes catalase and glutathione peroxidase, and a depletion of the content of the cellular glutathione peroxidase substrate GSH. The p38 pathway was significantly involved in the sustained oxidative stress to the cells. Taken together, the alteration of the antioxidant enzyme activities, in particular the peroxide-scavenging deficit, underlies the susceptibility to cell death in GMF-beta-overexpressing cells. In conclusion, we suggest that the proteinuria induction of GMF-beta in renal PT cells may play a critical role in the progression of renal diseases by enhancing oxidative injuries.

Cytotoxic necrotizing factor 1 enhances reactive oxygen species-dependent transcription and secretion of proinflammatory cytokines in human uroepithelial cells

Uropathogenic Escherichia coli strains frequently produce a Rho-activating protein toxin named cytotoxic necrotizing factor type 1 (CNF1). We herein report that CNF1 promotes transcription and release of tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), and IL-8 proinflammatory cytokines and increases the production of reactive oxygen species (ROS) in uroepithelial T24 cells. The antioxidant N-acetyl-L-cysteine counteracts these phenomena, a fact which suggests a role for ROS-mediated signaling in CNF1-induced proinflammatory cytokine production.

Proteasomal degradation of cytotoxic necrotizing factor 1-activated rac

The cytotoxic necrotizing factor 1 (CNF1) from Escherichia coli has been shown to activate members of the Rho family by deamidation of glutamine 63. This amino acid is essential for hydrolysis of GTP, and any substitution results in a constitutively active Rho. Activation of Rho induces the formation of stress fibers, filopodia, and membrane ruffles due to activation of RhoA, Cdc42, and Rac, respectively. Here we show that the level of endogenous Rac decreased in CNF1-treated HEK293 and HeLa cells. The amount of mRNA remained unaffected, leaving the possibility that Rac is subject to proteolytic degradation. Treatment of cells with lactacystin, an inhibitor of the 26S proteasome, protected Rac from degradation. We have previously shown that CNF1 activates the c-Jun N-terminal kinase (JNK) only transiently in HeLa cells (M. Lerm, J. Selzer, A. Hoffmeyer, U. R. Rapp, K. Aktories, and G. Schmidt, Infect. Immun. 67:496-503, 1998). Here we show that CNF1-induced JNK activation is stabilized in the presence of lactacystin. The data indicate that Rac is degraded by a proteasome-dependent pathway in CNF1-treated cells.

Critical role of reactive oxygen species formation in microcystin-induced cytoskeleton disruption in primary cultured hepatocytes

Cyanobacteria (blue-green algae)-contaminated water is a worldwide public health problem. Microcystins are a group of liver-specific toxins generated by cyanobacteria. It is generally believed that the protein phosphorylation that leads to the disruption of intermediate filaments plays an important role in microcystin-induced hepatotoxicity. However, the mechanisms that contribute to the microcystin-induced alterations of microtubules and microfilaments are not fully understood. In the present study, the effects of microcystin-fR (M-LR), the most common microcystin, were examined on the organization of cellular microtubules and microfilaments in primary cultured rat hepatocytes. Our results indicate that M-LR initiated reactive oxygen species (ROS) formation followed by altering the cytoskeleton structures, which eventually led to significant LDH leakage. These effects were completely prevented by TEMPOL, a superoxide dismutase mimic, and also partially prevented by desferoxamine. These findings provide further evidence that ROS formation, especially superoxide radical, plays a crucial role in M-LR-induced disruption of cytoskeleton organization and consequent hepatotoxicity.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.

Effect of redox modulation on xenogeneic target cells: the combination of nitric oxide and thiol deprivation protects porcine endothelial cells from lysis by IL-2-activated human NK cells

Evidence suggests that NK cells contribute to the pathogenesis of delayed rejection of vascularized xenografts, and NK cells have been suggested to participate in hyperacute xenograft rejection. Endothelial cells have been shown to be the primary target of the recipient's immune responses that mediate both hyperacute and delayed xenograft rejection. Under conditions of oxidative stress induced by thiol deprivation, but not under normal conditions, pretreatment of porcine aortic endothelial cells (PAECs) with the NO donor, S-nitroso-N-acetyl-penicillamine, dramatically inhibited killing of PAEC target cells by IL-2-activated human NK cells. This same combined treatment reduced both surface expression and mRNA levels of E-selectin. Moreover, anti-E-selectin mAb, but not Ab to VCAM-1, protected PAEC from lysis by human IL-2-activated NK cells in a dose-dependent manner. These findings suggest that expression of porcine E-selectin is important for the cytotoxicity of PAEC mediated by activated human NK cells and may be involved in the redox-mediated modulation of that cytotoxicity. It is known that NF-kappa B activation is required for transcription of E-selectin, and the current data show that the suppression of E-selectin expression by S-nitroso-N-acetyl-penicillamine pretreatment and thiol deprivation was associated with reduced NF-kappa B DNA-binding activity in PAEC. These data suggest that the regulation of porcine E-selectin may be important for modulating delayed xenograft rejection and that manipulation of cellular redox systems may provide a means to protect xenogeneic endothelial cells from NK cell-mediated cytotoxicity.