Intestinal perfusion of dietary levels of aluminium: association with the mucosa

Gene/environment interaction in the susceptibility of Crohn's disease patients to aluminum

BACKGROUND & AIM

The key role of environmental factors in the pathogenesis of Inflammatory Bowel Diseases (IBD) is recognized. Aluminum is suspected to be a risk factor for IBD. However, mechanisms linking aluminum exposure to disease development are unknown. We examined the role of aluminum transport and subcellular localisation on human colon susceptibility to aluminum-induced inflammation.

METHODS

Human colon biopsies isolated from Crohn's disease (CD) or control patients and Caco-2 cells were incubated with aluminum. The effects of aluminum were evaluated on cytokine secretion and transporter expression. The role of aluminum kinetics parameters was studied in Caco-2 using transport inhibitors and in human colon biopsies by assessing genetic polymorphisms of transporters.

RESULTS

Aluminum exposure was shown to induce cytokine secretion in colon of CD but not healthy patients. In Caco-2 cells, aluminum internalisation was correlated with inflammatory status. In human colon, analysis of genetic polymorphisms and expression of ABCB1 and SLC26A3 transporters showed that their decreased activity was involved in aluminum-induced inflammation.

CONCLUSIONS

We hypothesize that alteration in detoxifying response would lead to a deregulation of intestinal homeostasis and to the expression of IBD. Our study emphasizes the complexity of gene/environment interaction for aluminum adverse health effect, highlighting at risk populations or subtypes of patients. A better understanding of correlations between gene expression or SNP and xenobiotic kinetics parameters would shift the medical paradigm to more personalized disease management and treatment.

Elevated IgG Antibody to Aluminum Bound to Human Serum Albumin in Patients with Crohn's, Celiac and Alzheimer's Disease

Aluminum is in our water and food, and is used as an adjuvant in vaccines. About 40% of the ingested dose accumulates within the intestinal mucosa, making the gut the main target of inflammation and autoimmunity; about 1% accumulates in the skeletal system and brain, inducing the cross-linking of amyloid-β-42 peptide and the formation of amyloid aggregates associated with Alzheimer's disease. To examine whether the accumulation of aluminum in the gut and brain tissues results in neoantigen formation, we bound aluminum compounds to human serum albumin. We used ELISA to measure IgG antibody in 94 different sera from healthy controls and 47 sera from each group of patients: anti-Saccharomyces cerevisiae antibody-positive (Crohn's), and positive for deamidated α-gliadin and transglutaminase-2 IgA antibodies (celiac disease), autoimmune disorders associated with intestinal tissue antigens. Because earlier studies have shown that aluminum exposure is linked to Alzheimer's disease etiology, and high aluminum content is detected in Alzheimer's patients' brain tissue, we also measured aluminum antibody in the blood of these patients. Additionally, we measured aluminum antibody in the sera of mixed connective tissue disease patients who were positive for antinuclear antibodies, and used them as disease controls. We found significant IgG antibody elevation against all three aluminum compounds in the sera of patients with Crohn's, celiac and Alzheimer's disease, but not in patients with mixed connective tissue disease. We concluded that aluminum ingestion and absorption from the GI tract and brain may contribute to Crohn's, celiac and Alzheimer's disease, but not to mixed connective tissue disease.

Influence of aluminum salts on COVID-19 infected patients

Background/aim

Based on the antiviral and antibacterial properties of aluminum salts, we aimed to find out the influence of aluminum salts on COVID-19 infected patients.

Materials and methods

We performed an observational retrospective cohort study which includes the patients diagnosed as COVID-19 and received aluminum salts in addition to actual treatments during hospitalization as the treatment group (Alum Group). Patients who received standard COVID-19 treatment protocols in the Infectious Diseases Clinics were included as the Control Group. Clinical findings, laboratory parameters, length of stay, survival, radiological follow-up, intensive care and mechanical ventilation needs, the presence of comorbidity, polymerase chain reaction (PCR) tests, symptoms, symptom recovery times, hospital stay times, treatment protocols, and clinical presence of pneumonia were examined in all patients. Advanced chemical composition analyzes of existing aluminum salts were also performed.

Results

A total of 109 patients, 54 in the alum group and 55 in the control group, were included in the study. None of the patients in the aluminum group developed side effects due to the intake of aluminum salt. Survival status was significantly different between the two groups as there were 5 loss in the Control Group and none in the Alum Group (P = 0.023). The symptom recovery time was significantly shorter in the Alum Group; 2 (1–3) vs. 1 (1–2) days, P = 0.003. According to the paired samples analyses of the comparison between hospitalization and discharge, CRP levels significantly drops in the Alum Group (from 54.09 to 27, P = 0.001) but not in the Control Group. The drop was significantly same for the lactate dehydrogenase (LDH) and procalcitonin levels with P = 0.001.

Conclusion

It has been observed that aluminum salts have beneficial effects in COVID-19 infected cases. Considering the low systemic toxicity of intermittent oral intake of aluminum salts as food supplements and the fact that pandemic control is still not achieved, the use of aluminum salts is promising.

Metabolomic analysis reveals the mechanism of aluminum cytotoxicity in HT-29 cells

BACKGROUND

Aluminum (Al) is toxic to animals and humans. The most common sources of human exposure to Al are food and beverages. The intestinal epithelium is the first barrier against Al-induced toxicity. In this study, HT-29, a human colon cancer cell line, was selected as an in vitro model to evaluate the Al-induced alteration in metabolomic profiles and explore the possible mechanisms of Al toxicity.

METHODS

MTT assay was performed to determine the half-maximal inhibitory concentration of Al ions. Liquid chromatography-mass spectrometry (LC-MS) was used for metabolomic analysis, and its results were further confirmed using quantitative reverse transcription polymerase chain reaction (RT-qPCR) of nine selected genes.

RESULTS

Al inhibited the growth of the HT-29 cells, and its half-maximal dose for the inhibition of cell proliferation was found to be four mM. This dose was selected for further metabolomic analysis, which revealed that 81 metabolites, such glutathione (GSH), phosphatidylcholines, phosphatidylethanolamines, and creatine, and 17 metabolic pathways, such as the tricarboxylic acid cycle, pyruvate metabolism, and GSH metabolism, were significantly altered after Al exposure. The RT-qPCR results further confirmed these findings.

CONCLUSION

The metabolomics and RT-qPCR results indicate that the mechanisms of Al-induced cytotoxicity in HT-29 cells include cellular apoptosis, oxidative stress, and alteration of lipid, energy, and amino acid metabolism.

Dietary Lactobacillus plantarum supplementation enhances growth performance and alleviates aluminum toxicity in tilapia

We investigated the protection offered by the probiotic Lactobacillus plantarum CCFM639 against waterborne Al exposure in tilapia. Fish were allocated to control, CCFM639-only, Al-only or Al plus CCFM639 groups. The fish were exposed to 2.73mg/L Al ions for 4 weeks. The probiotic was incorporated into the fish diet at 10⁸ CFU/g and provided twice daily. Our results showed that L. plantarum CCFM639 significantly enhanced feed utilization, growth performance and antioxidant ability in the absence of waterborne Al exposure. When fish were exposed to Al, dietary supplementation with the strain effectively decreased the death rate and accumulation of Al in tissues, and enhanced growth performance. Moreover, Al-induced changes in hematobiochemical parameters and hepatic oxidative stress and histopathology were also alleviated. Therefore, L. plantarum CCFM639 may be a novel dietary supplement for fish to enhance growth performance and prevent aquaculture and food safety problems induced by Al pollution.

Potential of Lactobacillus plantarum CCFM639 in Protecting against Aluminum Toxicity Mediated by Intestinal Barrier Function and Oxidative Stress

Aluminum (Al) is a ubiquitous metal that can seriously harm the health of animals and humans. In our previous study, we demonstrated that Lactobacillus plantarum CCFM639 can decrease Al burden in the tissues of mice by inhibiting intestinal Al absorption. The main aim of the present research was to investigate whether the protection by the strain is also associated with enhancement of the intestinal barrier, alleviation of oxidative stress and modulation of the inflammatory response. In an in vitro cell model, two protection modes (intervention and therapy) were examined and the results indicated that L. plantarum CCFM639 alleviated Al-induced cytotoxicity. In a mouse model, L. plantarum CCFM639 treatment was found to significantly alleviate oxidative stress in the intestinal tract, regulate the function of the intestinal mucosal immune system, restore the integrity of tight junction proteins and maintain intestinal permeability. These results suggest that in addition to Al sequestration, L. plantarum CCFM639 can also inhibit Al absorption by protecting the intestinal barrier, alleviating Al-induced oxidative stress and inflammatory response. Therefore, L. plantarum CCFM639 has the potential to be a dietary supplement ingredient that provides protection against Al-induced gut injury.

Gut: An underestimated target organ for Aluminum

Since World War II, several factors such as an impressive industrial growth, an enhanced environmental bioavailability and intensified food consumption have contributed to a significant amplification of human exposure to aluminum. Aluminum is particularly present in food, beverages, some drugs and airbone dust. In our food, aluminum is superimposed via additives and cooking utensils. Therefore, the tolerable intake of aluminum is exceeded for a significant part of the world population, especially in children who are more vulnerable to toxic effects of pollutants than adults. Faced with this oral aluminum influx, intestinal tract is an essential barrier, especially as 38% of ingested aluminum accumulates at the intestinal mucosa. Although still poorly documented to date, the impact of oral exposure to aluminum in conditions relevant to real human exposure appears to be deleterious for gut homeostasis. Aluminum ingestion affects the regulation of the permeability, the microflora and the immune function of intestine. Nowadays, several arguments are consistent with an involvement of aluminum as an environmental risk factor for inflammatory bowel diseases.

Aluminum enhances inflammation and decreases mucosal healing in experimental colitis in mice

The increasing incidence of inflammatory bowel diseases (IBDs) in developing countries has highlighted the critical role of environmental pollutants as causative factors in their pathophysiology. Despite its ubiquity and immune toxicity, the impact of aluminum in the gut is not known. This study aimed to evaluate the effects of environmentally relevant intoxication with aluminum in murine models of colitis and to explore the underlying mechanisms. Oral administration of aluminum worsened intestinal inflammation in mice with 2,4,6-trinitrobenzene sulfonic acid- and dextran sodium sulfate-induced colitis and chronic colitis in interleukin 10-negative (IL10(-/-)) mice. Aluminum increased the intensity and duration of macroscopic and histologic inflammation, colonic myeloperoxidase activity, inflammatory cytokines expression, and decreased the epithelial cell renewal compared with control animals. Under basal conditions, aluminum impaired intestinal barrier function. In vitro, aluminum induced granuloma formation and synergized with lipopolysaccharide to stimulate inflammatory cytokines expression by epithelial cells. Deleterious effects of aluminum on intestinal inflammation and mucosal repair strongly suggest that aluminum might be an environmental IBD risk factor.

Origin and fate of dietary nanoparticles and microparticles in the gastrointestinal tract

Humans have evolved with oral exposure to dietary microparticles and nanoparticles as a normal occurrence but the ever-growing exploitation of nanotechnology is likely to increase exposure further, both qualitatively and quantitatively. Moreover, unlike the situation with respirable particles, relatively little is known about gastrointestinal intake and handling of nanoparticles. With a long term interest in gut exposure and responses to dietary microparticles, our group is now applying its expertise to nanoparticles in the gastrointestinal tract. Here we aim to address (i) the current challenges associated with the characterisation of particle-host or particle-cell interactions, (ii) the origin and mechanisms of uptake of particles in the gastrointestinal tract, especially via the Peyer's patch and (iii) potential cellular effects of nanoparticles in the generation of reactive oxygen species and inflammasome activation, or microparticles in their adjuvant activity in pro-inflammatory signalling and immune responsiveness.

The Chemical Species of Aluminum Influences Its Paracellular Flux across and Uptake into Caco-2 Cells, a Model of Gastrointestinal Absorption

Aluminum (Al) can cause neurotoxicity, a low-turnover osteomalacia, and microcytic anemia. To test the null hypothesis that the chemical form (species) of Al does not influence its mechanism or rate of absorption from the gastrointestinal tract, Al flux across and uptake into Caco-2 cells was investigated. Caco-2 cells were grown on porous membranes mounted in vertical diffusion chambers or in 35-mm-diameter plastic cell culture dishes. When 8 mM 27Al was introduced as the ion, citrate, maltolate, fluoride, or hydroxide, the apical to basolateral apparent permeability (Papp) of Al correlated highly with the Papp of lucifer yellow (LY), a paracellular marker, except when introduced as Al hydroxide. The uptake rate of Al when introduced as the fluoride was > when introduced as the ion > maltolate > citrate > hydroxide. The activation energy of Al introduced as the ion, citrate, maltolate, and fluoride, determined from Arrhenius plots, was 13-22 KJ/mol, suggesting diffusion-mediated uptake. With exposure to 2 microM Al (containing 26Al as a tracer) introduced as the ion, hydroxide, citrate, and fluoride, Al and LY Papp were consistent with results obtained with 8 mM Al, but were not Al species dependent. Approximately 0.015% of the 26Al fluxed across the cell monolayer; 0.75% was associated with cells. Lumogallion staining imaged by confocal laser microscopy showed Al co-localized with DAPI in the nucleus. The results suggest that (1) soluble Al species predominantly diffuse through the paracellular pathway, (2) the ligand-dependent flux rate of Al is due to an effect on the tight junctions, (3) Caco-2 cell uptake of Al is a diffusion process, and (4) the ligand can influence the rate of cellular Al uptake.

Structural modification and aggregation of mucin by chromium(III) complexes

Metal ions binding to proteins regulate the functions of proteins and may also lead to structural changes. In this communication we demonstrate the interaction and subsequent conformational changes induced in pig gastric mucin (PGM) upon binding to certain chromium(III) complexes like, [Cr(salen)(H(2)O)(2)](ClO(4)) (1), [Cr(en)(3)]Cl(3) (2) and [Cr(EDTA)(H(2)O)]Na (3) which vary in charge and ionic character. Complexes 1 and 3 have been shown to interact coordinately with PGM whereas complex 2 binds through electrostatic interaction and hydrogen bonding. Steady state fluorescence experiment reveals that at lower concentration of complex 2 there is partial quenching of the tyrosine emission, whereas at higher concentration of the complex the emission intensity is enhanced. On the other hand with complexes 1 and 3 a decrease in fluorescence intensity was observed. PGM viscosity was found to decrease in the presence of complex 1 and 3 due to the formation of flexible fibres through coordinate interaction. Complex 2 was found to facilitate metal induced intertangling of PGM fibres which tends to stabilize the interaction and leads to sol-gel transition with subsequent increase in viscosity. A significant change in CD spectrum of PGM was observed in the presence of complex 2, where random coil spectrum became typical of a alpha-helical structure with 80% alpha helix content. In the case of complexes 1 and 3 only minor changes in the amplitude of the spectrum were observed. Histochemical analysis supports the contention that complex 2 favors the oligomerisation of PGM and leads to the formation of aggregated mass of macromolecules.

Famotidine versus omeprazole, in combination with amoxycillin and tinidazole, for eradication of Helicobacter pylori infection

BACKGROUND

Eradication regimens combining two antibiotics with a proton pump inhibitor have been studied intensively. In contrast, only a few studies have focused on the possible role of H2-receptor antagonists in eradication therapy. The mechanism involved in the synergy between antibiotics and proton pump inhibitors is still controversial.

OBJECTIVES

To compare the results of two triple-therapy regimens, different only in the antisecretory drugs used, in patients with Helicobacter pylori infection, and to assess the impact of primary resistance to metronidazole on treatment outcome.

METHODS

A total of 120 patients with peptic ulcer and non-ulcer dyspepsia were randomly assigned to a 2-week course of either: famotidine 40 mg twice a day, amoxycillin 1 g twice a day and tinidazole 500 mg twice a day (FAT group; n = 60); or omeprazole 20 mg twice a day, amoxycillin 1 g twice a day and tinidazole 500 mg twice a day (OAT group; n = 60). Upper endoscopy was performed prior to treatment and at least 4 weeks after completion of treatment and discontinuation of the antisecretory therapy. H. pylori status was assessed by a biopsy urease test, histology and culture.

RESULTS

In the intention-to-treat analysis, eradication of H. pylori was achieved in 48 of the 60 patients (80%; 95% confidence interval: 70-90%) in the FAT group, compared to 50 of the 60 patients (83.3%; 95% confidence interval: 74-93%) in the OAT group. In the per protocol analysis, eradication therapy was achieved in 48 out of 53 patients (90.6%; 95% confidence interval: 83-98%) treated with FAT and 50 out of 57 patients (87.7%; 95% confidence interval: 79-96%) treated with OAT (not significant). The primary metronidazole resistance was present in 28.8% of strains. Overall, per protocol eradication rates in strains resistant and susceptible to metronidazole were 83.3% and 91.3% respectively (P > 0.05).

CONCLUSIONS

Two-week courses of either high-dose famotidine or omeprazole, both combined with amoxycillin and tinidazole, are equally effective for eradication of H. pylori infection. In a 2-week triple therapy, metronidazole resistance has no significant impact on eradication rates.

The precipitation of mucin by aluminium

The interactions of Al with a mucin glycopeptide have been studied. A number of specific reactions were identified the nature of which were dependent upon the Al chemistry in the hydration environment. In particular, Al was observed to precipitate mucin and it is suggested that this proceeded via the intercalation of the hydroxide within the hydrated macroreticular network of the mucin biopolymer. This precipitation of mucin was visible by eye and abolished the viscosity of native mucin. Viscometry indicated that Al was bound by mucin at low pH. At pH > 3 Al formed a low molecular weight complex with mucin which was hydrolytically stable and was not precipitated at pH up to 8. In an additional and competitive reaction Al was bound by mucin and the resultant mucin-Al complex was suggested to be the precursor to self-assembled mucin-Al spheres identified in solution, by photon correlation spectroscopy, and in precipitate using selective histochemistry. The majority of these spherical structures were of sub-micron diameter and, through their interaction with each other, were probably responsible for the observed pH-dependent peaks of mucin solution viscosity. The larger spheres, between 20 and 80 microns in diameter, were only identified in isolated mucin/Al precipitates and, being comparatively rare, were unlikely to have influenced solution viscosities. These large spheres were observed to act as possible nucleation sites for the flocculation of mucin/Al precipitate. Al at concentrations as low as 0.015 mM induced changes in the rheological properties of mucin. Considering the ubiquitous nature of mucin and the degree to which it is conserved within biota the interactions of Al with mucin may have wide ranging implications for biological systems.

Aluminum exposure and metabolism

Aluminum (Al) is a nonessential, toxic metal to which humans are frequently exposed. Oral exposure to aluminum occurs through ingestion of aluminum-containing pharmaceuticals and to a lesser extent foods and water. Parenteral exposure to aluminum can occur via contaminated total parenteral nutrition (TPN), intravenous (i.v.) solutions, or contaminated dialysates. Inhalation exposure may be important in some occupational settings. The gut is the most effective organ in preventing tissue aluminum accumulation after oral exposure. Typically gastrointestinal absorption of aluminum from diets is < 1%. Although the mechanisms of aluminum absorption have not been elucidated, both passive and active transcellular processes and paracellular transport are believed to occur. Aluminum and calcium may share some absorptive pathways. Aluminum absorption is also affected by the speciation of aluminum and a variety of other substances, including citrate, in the gut milieu. Not all absorbed or parenterally delivered aluminum is excreted in urine. Low glomerular filtration of aluminum reflects that most aluminum in plasma is nonfiltrable because of complexation to proteins, predominantly transferrin. The importance of biliary secretion of aluminum is debatable and the mechanism(s) is poorly understood and appears to be saturable by fairly low oral doses of aluminum.

Pooled analysis of anti-Helicobacter pylori treatment regimens

BACKGROUND

The human pathogen Helicobacter pylori and its association with peptic ulcer has dramatically changed the therapeutic approach to patients with this disease. Successful treatment of the infection has consistently been shown to prevent ulcer recurrence. Published data on therapeutic options are sometimes confusing since only few studies have similar design, drug combinations, dosage, dosing, formulation, patient material, and size. A formal meta-analysis is therefore of limited value.

METHOD

Data on anti-H. pylori therapies from a large number of publications are pooled into a few groups based on the combination of drugs, regardless of dosage, duration, etc., of the therapy. A mean success rate is calculated for all studies with subanalysis with regard to study design, size, doses and duration.

RESULTS

Triple combinations are needed to achieve a success rate of more than 80%. Bismuth/tetracycline based triple therapy gives 82% success rate (range 43-100%) compared to 85% and 87% success rate (range 72-100% and 43-100%) achieved with omeprazole/clarithromycin based triples respectively.

CONCLUSION

Omeprazole/clarithromycin based triple regimens are the most effective anti-H. pylori therapeutic strategies, slightly superior to bismuth triple regimens.

Dual and triple therapy regimens of antisecretory agents and antibiotics for the eradication of Helicobacter pylori: an overview

BACKGROUND

Studies evaluating therapeutic regimens that combine antisecretory agents with antibiotics for the eradication of H. pylori have reported significant variations in efficacy.

METHODS

We reviewed the published literature to compare H. pylori eradication rates in patients treated with either omeprazole, ranitidine bismuth citrate (RBC), or ranitidine plus metronidazole combined with either amoxicillin or clarithromycin.

RESULTS

Wide variations in H. pylori eradication rates have been reported with omeprazole plus either amoxicillin (0-100%) or clarithromycin (42-88%). Eradication rates ranging from 45% to 89% and from 74% to 94% have been reported with RBC plus either amoxicillin or clarithromycin, respectively. Eradication rates ranging from 48% to 90% have been reported with ranitidine plus metronidazole and amoxicillin and one study reported an eradication rate of 95% with ranitidine plus metronidazole and clarithromycin

CONCLUSIONS

Well-controlled trials with ranitidine bismuth citrate plus clarithromycin suggest that this combination may provide the most consistent and effective regimen for the eradication of H. pylori infection.