Dose-response relationships in aluminium toxicity in humans.

INTRODUCTION: Aluminium exposure is associated with bone disease (an elevated bone content of aluminium and reduced bone formation on bone biopsy) and neurotoxicity (features of altered brain functions and/or typical spike and slow wave waveforms on electroencephalogram) in patients with elevated blood aluminium concentrations. OBJECTIVES: To critically analyse the literature to determine the dose-toxicity relationships between aluminium exposure and related bone disease and aluminium neurotoxicity. METHODS: A systematic review of the literature with collation and analysis of individual data of human cases of aluminium exposure was conducted between 1 January 1966 and 30 December 2020. Embase, MEDLINE (OVID MEDLINE), PubMed and TOXNET were searched with the following strategies: "Aluminium AND toxicity OR aluminium AND poisoning OR aluminium AND dialysis OR aluminium AND chronic renal failure OR aluminium AND intravenous" limited to "(human)". Inclusion criteria required individual data relating to aluminium exposure in humans. Papers in which features of aluminium toxicity and analytical confirmation of aluminium exposure could not be determined in individual patients were excluded. RESULTS: Thirty-seven papers were identified, which included data on 179 individuals exposed to aluminium. The sources of aluminium exposure (median duration of exposure) were: dialysis fluid (48 months) in 110 cases; oral aluminium hydroxide (20 months) in 20 cases; plasma exchange (2 months) in 16 cases; infant formula feed (minimal duration of 2 weeks) in 14 cases; intravesical exposures (2 days) in 13 oncology patients and potable water exposure in six cases. EXPOSURE TO DIALYSIS FLUID: Of the 110 patients exposed to dialysis fluid, 99 were adults and 11 children, who were analysed separated. Of the adults, 50 with aluminium neurotoxicity had a median aluminium concentration of 467 µg/L (IQR 230 - 752), 28 with aluminium bone disease had a median aluminium concentration of 142 µg/L (IQR 46-309) and 21 with asymptomatic aluminium overload had a median aluminium concentration of 35 µg/L (IQR 26-51). Median aluminium concentrations were significantly greater in patients with aluminium neurotoxicity compared to those with aluminium bone disease (p < 0.0001) or asymptomatic aluminium overload (p < 0.0001). ORAL ALUMINIUM HYDROXIDE: Of the 20 cases, 11 were adults and nine were children. Of the 11 adults, eight with aluminium neurotoxicity had a median aluminium concentration of 682 µg/L (IQR 438-770) and three with aluminium bone disease had a median aluminium concentration of 100 µg/L (IQR 62-138) (p = 0.007). Of the nine children, five had aluminium neurotoxicity with a median aluminium concentration of 335 µg/L (IQR 229-601), one had aluminium bone disease and an aluminium concentration of 1030 µg/L and three had asymptomatic aluminium overload with a median aluminium concentration 98 µg/L (IQR 65-365). PLASMA EXCHANGE: Three patients with stage 5 chronic kidney disease developed aluminium bone disease during plasma exchange; their median blood or serum aluminium concentration was 73 µg/L (IQR 59-81). Asymptomatic aluminium overload was reported in six patients receiving outpatient plasma exchange who had a median creatinine clearance of 71 mL/min (IQR 40-106) and a median aluminium concentration of 49 µg/L (IQR 34-116), and in seven intensive care patients with acute kidney injury whose median aluminium concentration was 30 µg/L (IQR 17-35); (p = 0.02). INTRAVESICAL EXPOSURES: All 13 intravesical exposures developed aluminium neurotoxicity and had a median aluminium concentration of 157 µg/L (IQR 45-276). POTABLE WATER: All six patients developed aluminium bone disease and their median blood aluminium concentration was 17 µg/L (IQR 13-100). CONCLUSIONS: Toxic aluminium exposure can result in neurotoxicity and bone disease, especially in patients with chronic kidney disease. Adults with stage 5 chronic kidney disease chronically exposed to aluminium developed aluminium neurotoxicity at higher concentrations than those with aluminium bone disease or with asymptomatic aluminium overload. Aluminium neurotoxicity was reported at lower concentrations following acute exposure to intravesical aluminium. Extrapolating the relevance of these concentrations to the general population is problematic in that the data were derived from oncology patients, however, the possibility that aluminium neurotoxicity may occur at concentrations lower that those reported historically in patients with stage 5 chronic kidney disease cannot be excluded.

Bystander killing of melanoma cells using the human tyrosinase promoter to express the Escherichia coli purine nucleoside phosphorylase gene.

We used a gene transfer-based system to generate highly toxic purine bases in tumor cells transfected with the Escherichia coli purine nucleoside phosphorylase (PNP) gene. Because these toxic purines are membrane permeant, they mediate effective killing of neighboring cells that do not express E. coli PNP ("bystander" toxicity). In mixed cultures containing increasing percentages of cells with gene expression, 100% cancer cell growth arrest and total population killing was demonstrated when as few as 1-2% of cells expressed E. coli PNP. We used E. coli PNP to test bystander killing of human melanoma cells. A 529-bp region upstream of the human tyrosinase gene start site was shown to direct melanoma-specific expression in human cell lines. When this human tyrosinase regulatory region was used to control E. coli PNP expression, profound toxicity was observed in melanoma cells after treatment with the relatively nontoxic substrate 6-methylpurine-deoxyriboside, which is converted by E. coli PNP into the highly toxic purine base 6-methylpurine. Bystander toxicity was estimated as at least 100 cells killed for each cell expressing E. coli PNP, a level substantially higher than that of other tumor sensitization genes currently being used in clinical trails. These results suggest that the high bystander activity of the system could lead to significant antimelanoma responses in vivo.

Environmental factors in the development of autism spectrum disorders.

Autism spectrum disorders (ASD) are highly heterogeneous developmental conditions characterized by deficits in social interaction, verbal and nonverbal communication, and obsessive/stereotyped patterns of behavior and repetitive movements. Social interaction impairments are the most characteristic deficits in ASD. There is also evidence of impoverished language and empathy, a profound inability to use standard nonverbal behaviors (eye contact, affective expression) to regulate social interactions with others, difficulties in showing empathy, failure to share enjoyment, interests and achievements with others, and a lack of social and emotional reciprocity. In developed countries, it is now reported that 1%-1.5% of children have ASD, and in the US 2015 CDC reports that approximately one in 45 children suffer from ASD. Despite the intense research focus on ASD in the last decade, the underlying etiology remains unknown. Genetic research involving twins and family studies strongly supports a significant contribution of environmental factors in addition to genetic factors in ASD etiology. A comprehensive literature search has implicated several environmental factors associated with the development of ASD. These include pesticides, phthalates, polychlorinated biphenyls, solvents, air pollutants, fragrances, glyphosate and heavy metals, especially aluminum used in vaccines as adjuvant. Importantly, the majority of these toxicants are some of the most common ingredients in cosmetics and herbicides to which almost all of us are regularly exposed to in the form of fragrances, face makeup, cologne, air fresheners, food flavors, detergents, insecticides and herbicides. In this review we describe various scientific data to show the role of environmental factors in ASD.

Influence of adjuvants on the quantity, affinity, isotype and epitope specificity of murine antibodies.

Five adjuvants were compared to Freund's adjuvant for production of mouse polyclonal antibodies and monoclonal antibodies (McAbs) to human serum albumin (HSA) and interleukin-1 alpha (IL-1 alpha). Parameters examined were titer, affinity, concentration, isotype, epitope specificity and neutralizing activity of sera and hybridoma supernatants. Freund's adjuvant, while producing high titers and concentrations of antibodies in sera, was inferior to other adjuvants for eliciting antibodies with particular qualities. The adjuvants Quil A and A1(OH)3/[Thr1]muramyldipeptide elicited the highest affinity antibodies to HSA. Syntex adjuvant formulation-1 (SAF-1) elicited the highest percentage of 'protective' IgG2a antibodies to HSA. All adjuvants, particularly Quil A and Ribi adjuvant system, where superior to Freund's adjuvant in eliciting antibodies which bound native versus denatured HSA. In a comparison of SAF-1 and Freund's adjuvant, SAF-1 was superior to Freund's adjuvant in eliciting polyclonal and hybridoma antibodies which neutralized the biological activity of IL-1 alpha. These results show that adjuvants selectively and independently enhance different qualities of the antibody response. Furthermore, immunization with the appropriate adjuvant can optimize production of McAbs with desired qualities.

Morphological diversity of ependymal cells in tissue culture.

Ependymal cells were visualized in primary cultures of cerebral cortex from rat using an immunohistochemical staining technique. Five different morphological subtypes of cuboidal ependyma were recognized: 1) round, 2) triangular, 3) columnar, 4) cone- and spindle-shaped, and 5) large pleomorphic cells. These cells varied in size and almost all possessed cilia. Two distinct forms of tanycyte ependyma were detected based on the presence of cilia. These features reflect a significant level of development of the ependymal cells in culture and may correspond to functional diversity within this group.

Rilmenidine-induced ocular hypotension: role of imidazoline1 and alpha 2 receptors.

PURPOSE: To examine ocular actions by rilmenidine, an imidazoline1 and alpha 2 adrenoceptor agonist. METHODS: Intraocular pressure was measured in normal and sympathetically denervated rabbits by pneumatonometry. Electrically stimulated 3H-norepinephrine release from sympathetic nerves was determined in isolated, perfused rabbit iris-ciliary bodies. cAMP levels were evaluated in rabbit iris-ciliary bodies by radioimmunoassay. Ca2+ concentrations were measured in rabbit transformed nonpigmented ciliary epithelial cells by fluorescence ratio microscopy. RESULTS: Topical, unilateral administration of rilmenidine produced hypotensive responses in normal rabbits which were antagonized by either bilaterally administered efaroxan, an imidazoline receptor antagonist or rauwolscine, an alpha 2 receptor antagonist. Sympathectomy also eliminated the ocular hypotensive response. Rilmenidine (0.001, 0.01, 0.1, 1 microM) caused 5 +/- 1%, 18 +/- 5%, 35 +/- 10%, and 48 +/- 9% inhibition, respectively, of 3H-norepinephrine overflow whereas 10 microM efaroxan or rauwolscine caused enhancement of norepinephrine release by 102 +/- 23% or 86 +/- 25%, respectively. Furthermore, pretreatment with efaroxan or rauwolscine partially antagonized the inhibition of norepinephrine release induced by rilmenidine. In other experiments, rilmenidine (1 microM) inhibited isoproterenol-stimulated cAMP accumulation in rabbit iris-ciliary bodies by 43 +/- 9% which was antagonized by 10 microM efaroxan or rauwolscine. Rilmenidine induced large increases in [Ca2+]i in rabbit nonpigmented ciliary epithelial cells which were effectively antagonized by efaroxan or rauwolscine. CONCLUSIONS: These in vivo and in vitro data suggest that the ocular hypotensive activity induced by rilmenidine is due, in part, to suppression of sympathetic neuroeffector function in the rabbit ciliary body and that alpha 2 adrenergic receptors and/or imidazoline1 receptors are involved.

Cell to cell contact is not required for bystander cell killing by Escherichia coli purine nucleoside phosphorylase.

Expression of Escherichia coli purine nucleoside phosphorylase (PNP) activates prodrugs and kills entire populations of mammalian cells, even when as few as 1% of the cells express this gene. This phenomenon of bystander killing has been previously investigated for herpes simplex virus-thymidine kinase (HSV-TK) and has been shown to require cell to cell contact. Using silicon rings to separate E. coli PNP expressing cells from non-expressing cells sharing the same medium, we demonstrate that bystander cell killing by E. coli PNP does not require cell-cell contact. Initially, cells expressing E. coli PNP convert the non-toxic prodrug, 6-methylpurine-2'-deoxyriboside (MeP-dR) to the highly toxic membrane permeable toxin, 6-methylpurine (MeP). As the expressing cells die, E. coli PNP is released into the culture medium, retains activity, and continues precursor conversion extracellularly (as determined by reverse phase high performance liquid chromatography of both prodrug and toxin). Bystander killing can also be observed in the absence of extracellular E. coli PNP by removing the MeP-dR prior to death of the expressing cells. In this case, 100% of cultured cells die when as few as 3% of the cells of a population express E. coli PNP. Blocking nucleoside transport with nitrobenzylthioinosine reduces MeP-dR mediated cell killing but not MeP cell killing. These mechanisms differ fundamentally from those previously reported for the HSV-TK gene.

Efficiency of plasmid delivery and expression after lipid-mediated gene transfer to human cells in vitro.

Cationic liposome-mediated gene transfer has become increasingly important in the development of experimental therapies for human diseases, such as melanoma, human immunodeficiency virus infection, cystic fibrosis and alpha-1 antitrypsin deficiency. However, very little is known about the mechanisms by which lipid-mediated gene transfer occurs. We studied the kinetics of plasmid delivery and expression by using this technique. Plasmid entry in the cystic fibrosis respiratory epithelial cell line 2CFSME0-1 as well as in two other cell lines (HeP 2g and HeLa) occurred in 95 to 100% of cells within 1 hr of the initiation of lipid-mediated gene transfer. In hepatic and respiratory cells, transcription of a construct containing the cystic fibrosis transmembrane conductance regulator was observed in more than 80% of the cell population; similarly high levels of plasmid utilization were obtained in studies of HLA-B7 expression in human melanoma cells. Studies directly relevant to current human trials of lipid-mediated gene transfer indicate that plasmid entry, transcription and translation are often surprisingly efficient, and may occur in nearly 100% of human cells in culture when sensitive methods for detection are used. Furthermore, conventional X-gal immunohistochemistry markedly underestimates transfection efficiency during transient gene expression. These studies point to a new mechanistic understanding of the features that limit expression by using cationic liposomes.