Intrinsic Toxic Effect Research Articles

Active immunization combined with cisplatin confers enhanced therapeutic protection and prevents relapses of HPV-induced tumors at different anatomical sites.

The active immunotherapy concept relies on the use of vaccines that are capable of inducing antitumor immunity, reversion of the suppressive immunological environment, and long-term memory responses. Previously, antitumor vaccines based on a recombinant plasmid (pgDE7h) or a purified protein (gDE7) led to regression of early-established human papillomavirus (HPV)-associated tumors in a preclinical model. In this work, the anticancer vaccines were combined with cisplatin to treat HPV-induced tumors at advanced growth stages. The antitumor effects were evaluated in terms of tumor regression, induction of specific CD8+ T cells, and immune modulation of the tumor microenvironment. Acute toxicity induced by the treatment was measured by weight loss and histological alterations in the liver and kidneys. Our results revealed that the combination of cisplatin with either one of the tested immunotherapies (pgDE7h or gDE7) led to complete tumor regression in mice. Also, the combined treatment resulted in synergistic effects, particularly among mice immunized with gDE7, including activation of systemic and tumor-infiltrating E7-specific CD8+ T cells, tumor infiltration of macrophages and dendritic cells, and prevention of tumor relapses at different anatomical sites. Furthermore, the protocol allowed the reduction of cisplatin dosage and its intrinsic toxic effects, without reducing antitumor outcomes. These results expand our knowledge of active immunotherapy protocols and open perspectives for alternative treatments of HPV-associated tumors.

A critical review on microbe-electrode interactions towards heavy metal ion detection using microbial fuel cell technology

Implicit interaction of electroactive microbes with solid electrodes is an interesting phenomenon in nature, which supported development of bioelectrochemical systems (BESs), especially the microbial fuel cell (MFCs) for valorization of low-value waste streams into bioelectricity. Intriguingly, the metabolism of interacted microbes with electrode is affected by the microenvironment at electrodes, which influences the current response. For instance, when heavy metal ions (HMIs) are imposed in the medium, the current production decreases due to their intrinsic toxic effect. This event provides an immense opportunity to utilize MFC as a sensor to selectively detect HMIs in the environment, which has been explored vastly in recent decade. In this review, we have concisely discussed the microbial interaction with electrodes and mechanism of detection of HMIs using an MFC. Recent advancement in sensing elements and their application is elaborated with a future perspective section for follow-up research and development in this field.

A Comparison between Neuromuscular Effects of Parathion and Paraoxon on Chick Biventer Cervicis Nerve-Muscle and the Reversal of their Effects by Pralidoxime

Background: It is generally believed that the anticholinesterase effect is induced by the organophosphate insecticide parathion only through its bioactive metabolite (i.e., paraoxon) that is created in the liver. Objectives: This study aimed to evaluate the intrinsic anticholinesterase effect of parathion, compared to its main metabolite. Methods: This study has been conducted to prepare the isolated chick biventer cervicis nerve-muscle using the twitch tension recording method. Results: According to the results, paraoxon (0.1 µM) induced a highly significant increase (more than 100%) in the twitch height, while higher concentrations (0.3 and 1 µM) induced partial or total contractures. Furthermore, parathion induced almost the same percentage of increase in the twitch height at 1 µM and partial or total contractures at 3 and 10 µM. It should be noted that pralidoxime (2-PAM), at 300 µM, reversed the effects of paraoxon and its parent (i.e., parathion). Conclusion: These results demonstrate that both parathion and its metabolite inhibit the acetylcholinesterase enzyme which can be reactivated by pralidoxime, whereas parathion is about 10 times less potent, compared to its metabolite. Therefore, the intrinsic toxic effects of parathion, regardless of its metabolite, should be considered in future studies.

Joint toxic impacts of cadmium and three pesticides on embryonic development of rare minnow (Gobiocypris rarus).

Although rare minnow (Gobiocypris rarus) has been employed in many toxicological investigations, most of them have only assessed the impacts of single chemical. In our current work, we investigated the single and joint toxic impacts of heavy metal cadmium (Cd) and three pesticides (thiamethoxam, bifenthrin, and tebuconazole) on G. rarus embryos. Results from the 96-h semi-static toxicity assay exhibited that bifenthrin possessed the highest intrinsic toxic effect on rare minnows with an LC50 value of 1.86mgL-1, followed by tebuconazole with LC50 values of 4.07mgL-1. Contrarily, thiamethoxam elicited the least toxic effect with an LC50 value of 351.9mgL-1. Seven chemical mixtures (four binary mixtures of Cd-bifenthrin, thiamethoxam-bifenthrin, thiamethoxam-tebuconazole, and bifenthrin-tebuconazole, two ternary mixtures of Cd-thiamethoxam-tebuconazole and thiamethoxam-bifenthrin-tebuconazole, and one quaternary mixture of Cd-thiamethoxam-bifenthrin-tebuconazole) displayed synergistic impacts with equivalent concentration and equitoxic ratio on G. rarus. Our results offered valuable insights into ecological risk assessment of these chemical combinations to aquatic vertebrates. The simultaneous existence of a few chemicals in the aquatic ecosystem might result in elevated toxicity, leading to severe harm to the non-target organisms compared with single compound. The observed synergistic interactions underlined the necessity to revise water quality standards, in which the detrimental joint effects of these chemicals are likely to be underestimated.

Palmitate lipotoxicity in enteric glial cells: Lipid remodeling and mitochondrial ROS are responsible for cyt c release outside mitochondria

Enteric glial cells (EGCs) are components of the enteric nervous system, an organized structure that controls gut functions. EGCs may be vulnerable to different agents, such as bacterial infections that could alter the intestinal epithelial barrier, allowing bacterial toxins and/or other agents possessing intrinsic toxic effect to access cells. Palmitate, known to exhibit lipotoxicity, is released in the gut during the digestion process. In this study, we investigated the lipotoxic effect of palmitate in cultured EGCs, with particular emphasis on palmitate-dependent intracellular lipid remodeling. Palmitate but not linoleate altered mitochondrial and endoplasmic reticulum lipid composition. In particular, the levels of phosphatidic acid, key precursor of phospholipid synthesis, increased, whereas those of mitochondrial cardiolipin (CL) decreased; in parallel, phospholipid remodeling was induced. CL remodeling (chains shortening and saturation) together with palmitate-triggered mitochondrial burst, caused cytochrome c (cyt c) detachment from its CL anchor and accumulation in the intermembrane space as soluble pool. Palmitate decreased mitochondrial membrane potential and ATP levels, without mPTP opening. Mitochondrial ROS permeation into the cytosol and palmitate-induced ER stress activated JNK and p38, culminating in Bim and Bax overexpression, factors known to increase the outer mitochondrial membrane permeability. Overall, in EGCs palmitate produced weakening of cyt c-CL interactions and favoured the egress of the soluble cyt c pool outside mitochondria to trigger caspase-3-dependent viability loss. Elucidating the mechanisms of palmitate lipotoxicity in EGCs may be relevant in gut pathological conditions occurring in vivo such as those following an insult that may damage the intestinal epithelial barrier.

A plasma cell differentiation quality control ablates B cell clones with biallelic Ig rearrangements and truncated Ig production

Aberrantly rearranged immunoglobulin (Ig) alleles are frequent. They are usually considered sterile and innocuous as a result of nonsense-mediated mRNA decay. However, alternative splicing can yield internally deleted proteins from such nonproductively V(D)J-rearranged loci. We show that nonsense codons from variable (V) Igκ exons promote exon-skipping and synthesis of V domain-less κ light chains (ΔV-κLCs). Unexpectedly, such ΔV-κLCs inhibit plasma cell (PC) differentiation. Accordingly, in wild-type mice, rearrangements encoding ΔV-κLCs are rare in PCs, but frequent in B cells. Likewise, enforcing expression of ΔV-κLCs impaired PC differentiation and antibody responses without disturbing germinal center reactions. In addition, PCs expressing ΔV-κLCs synthesize low levels of Ig and are mostly found among short-lived plasmablasts. ΔV-κLCs have intrinsic toxic effects in PCs unrelated to Ig assembly, but mediated by ER stress-associated apoptosis, making PCs producing ΔV-κLCs highly sensitive to proteasome inhibitors. Altogether, these findings demonstrate a quality control checkpoint blunting terminal PC differentiation by eliminating those cells expressing nonfunctionally rearranged Igκ alleles. This truncated Ig exclusion (TIE) checkpoint ablates PC clones with ΔV-κLCs production and exacerbated ER stress response. The TIE checkpoint thus mediates selection of long-lived PCs with limited ER stress supporting high Ig secretion, but with a cost in terms of antigen-independent narrowing of the repertoire.

Genotoxicity and Cytotoxicity Exerted by Pesticides in Different Biotic Matrices-An Overview of More Than a Decade of Experimental Evaluation

Agrochemicals represent one of the most important sources of environmental pollution. Although attempts to reduce agrochemical use through organic agricultural practices and the use of other technologies to control pests continue, the problem is still unsolved. Recent technological advances in molecular biology and analytical science have allowed the development of rapid, robust, and sensitive diagnostic tests (biomarkers) that can be used to monitor exposure to, and the effects of pollution. One of the major goals of our research laboratory is to evaluate comparatively the genotoxic and cytotoxic effects exerted by several pure agrochemicals and their technical formulations commonly used in Argentina on vertebrate cellsin vitro and in vivo employing several end-points for geno and cytotoxicity. Among them are listed the herbicides dicamba and flurochloridone, the fungicide zineb, the insecticides pirimicarb and imidacloprid. Overall, the results clearly demonstrated that the damage induced by the commercial formulations is in general greater than that produced by the pure pesticides, suggesting the presence of deleterious components in the excipients with either a putative intrinsic toxic effect or with the capacity of exacerbating the toxicity of the pure agrochemicals, or both. Accordingly, the results highlight that: 1) A complete knowledge of the toxic effect/s of the active ingredient is not enough in biomonitoring studies; 2) Pesticide/s toxic effect/s should be evaluated assaying to the commercial formulation available in market; 3) The deleterious effect/s of the excipient/s present within the commercial formulation should not be either discarded nor underestimated, and 4) A single bioassay is not enough to characterize the toxicity of a agrochemical under study.

Tracing the role of R-bodies in the killer trait: Absence of toxicity of R-body producing recombinant E. coli on paramecia

R-bodies are coiled proteinaceous ribbons produced by Paramecium endosymbionts belonging to the genus Caedibacter. These intracellular bacteria confer upon their hosts a phenomenon called the killer trait. It is the ability to kill symbiont-free competitors called sensitives. The R-body is the crucial element of this process, but despite many efforts, the actual role of R-bodies in killing sensitive paramecia is still not satisfactory clarified. The open question is whether the R-body acts as transmitter for a yet unidentified toxin or whether it directly kills sensitive paramecia having intrinsic cytotoxic effects. In the present study, this problem is addressed by heterologous expression of Caedibacter taeniospiralis R-body in Escherichia coli followed by a detailed analysis of its potential intrinsic toxic effect on feeding sensitive Paramecium tetraurelia. Using this approach, we can exclude any eventual effects of additional, unidentified factors produced by C. taeniospiralis and thus observe the impact of the recombinant R-body itself. No cytotoxic effects of recombinant R-bodies were detected following this approach, strengthening the hypothesis that R-bodies act as releasing system for an unidentified C. taeniospiralis toxin.

Urine excretion of protein HC in proteinuric glomerular diseases correlates to urine IgG but not to albuminuria

Proteinuric glomerular diseases often are associated with tubulointerstitial injury, which imposes on the progression of renal failure. Tubular damage is partly referable to toxic effects on the tubular epithelial cells induced by filtered plasma proteins. Patients with nonselective proteinuria, that is, increased urine excretion of high-molecular-weight plasma proteins such as IgG in comparison to albumin, often have poor renal outcome. The present observational study examined correlations between the degree of tubular damage, measured by urine concentration of protein HC, and the levels of urine IgG and albuminuria. Measurements of urine concentrations of IgG, albumin, and protein HC were performed in 56 proteinuric patients (33 males and 23 females) with nondiabetic glomerular diseases at the time of the diagnostic renal biopsy and at a mean of 49 follow-up months. A highly significant correlation between the urine IgG excretion and the urine protein HC concentration was found both at the start and at the end of the observational time (r = 0.74 and 0.65, respectively, P < 0.001). Furthermore, alterations in the urinary excretion of the two proteins in single patients correlated significantly to each other (r = 0.84, P < 0.001). The correlation between the degree of albuminuria and the protein HC excretion was significant at the time of kidney biopsy, but ceased to exist during the follow-up time. Stepwise linear regression analysis showed that in comparison with the creatinine clearance and albuminuria, only the changes in urinary IgG excretion were related to the corresponding changes in urinary protein HC excretion (r = 0.84 and r2 = 0.7, P < 0.001). The findings of the study suggest that the urinary protein HC concentration correlates to the degree of IgG-uria but not to the degree of albuminuria during the course of proteinuric glomerular disease. Whether this correlation is to be explained by an intrinsic toxic effect on tubular cells executed by IgG or perhaps by some other high molecular weight proteins, needs to be investigated further. However, the results contribute to the understanding of the poor renal survival in patients with glomerular diseases and nonselective proteinuria.

Modulation of the typical multidrug resistance phenotype by targeting the MED-1 region of human MDR1 promoter

Multidrug resistance of cancer (MDR) is the major cause of failure of chemotherapy. The typical MDR phenotype is due to the overexpression of membrane proteins among which the main representative is P-glycoprotein (Pgp) encoded by the MDR1 gene. Many attempts to modulate MDR by chemosensitizers have been unsuccessful in human therapy due to their intrinsic toxic effects. In an effort to modulate the MDR phenotype efficiently we designed an antisense and a transcriptional decoy strategy targeting the TATA-less human MDR1 gene promoter. The choice of the start point of transcription in a multiple start site window is related to an upstream MED-1 cis-element, the sequence and configuration of which are specific to human MDR1 gene expressed in Pgp-overproducing cancer cells. A 12mer antisense oligodeoxynucleotide (ODN) and a 12mer double-stranded ODN, both containing the MED-1 sequence, were designed and efficiently vectorized into the nucleus with the chimerical MPG peptide. A synthetic cellular model (NIH-EGFP) and highly resistant human CEM/VLB0.45 leukemia cells, significantly responded to transfection with the ODN/MPG complex. The level of EGFP fluorescence in NIH-EGFP cells decreased, and thus its production, and viability of CEM/VLB0.45 cells decreased by 63% in the presence of vinblastine, revealing that their resistance to the anticancer drug was reversed. These results open new insights into transcriptional decoy and anti-gene therapies of MDR cancers that overproduce Pgp. Gene Therapy (2000) 7, 1224-1233.

In vitro study for staining and toxicity of rose bengal on cultured bovine corneal endothelial cells.

It has recently been reported that rose bengal (RB) is actually not a vital dye and that it has an intrinsic toxic effect. Therefore, we conducted a study to determine its staining capability and the presence of intrinsic toxicity. We also examined its effects on the proliferation of cultured bovine corneal endothelial cells. The cells stained despite short exposure (1 s) to rose bengal under a fluorescein photomicroscope. The cell nucleus stained first, followed by the cytoplasm; the intensity was directly dependent on the exposure time. Although the entire cell layer did not stain at an RB concentration of 0.001%, the cell layer stained diffusely above a concentration of 0.01%. At a 5% concentration, areas of cellular detachment and lysis were noted. The degree of cellular change was directly proportional to the concentration of RB and the exposure time. Cellular damage included cell swelling, intracytoplasmic vacuole formation, cell detachment, and lysis. The presence of light augmented the toxic effect of RB on cultured endothelial cells and was statistically more significant than RB's intrinsic toxic effect. Exposure to RB concentrations > 0.01% induced statistically significant concentration-dependent inhibition of cell proliferation. These results suggest that rose bengal may not actually be a vital dye on cultured bovine corneal endothelial cells and that it has intrinsic inhibitory and toxic effects with additional phototoxic effects on corneal endothelial cells. Furthermore, cell proliferation was markedly inhibited after exposure to RB.

What is actually stained by rose bengal?

It has been believed that 1% rose bengal does not stain normal, healthy cells but rather stains degenerated or dead cells and mucous strands. In contrast to this conventional knowledge, we discovered that both commercial additive-containing and additive-free rose bengal solutions stained four different types of healthy cultured cells, including rabbit corneal epithelial cells. Rose bengal staining was rapid, dose dependent, predominantly nuclear, and detectable with the naked eye at concentrations as low as 0.05% and 0.025% for the commercial additive-containing or additive-free solutions, respectively, and with the fluorescence microscope at a concentration of 0.001%. It is surprising to discover that rose bengal is not a vital dye; after staining, cells actually lost vitality, as evidenced by instant morphologic changes, subsequent loss of cellular motility, cell detachment, and cell death. Such an intrinsic toxic effect was augmented by light exposure. The rose bengal staining of live as well as detergent-treated (Triton X-100) cells could be blocked by such tear components as mucin and albumin, suggesting that normally negative rose bengal staining is due to the protective function of the preocular tear film, ie, staining is not dictated by lack of cell vitality. These data indicate that rose bengal staining ensues whenever there is poor protection of surface epithelium by the preocular tear film; this represents a new interpretation for rose bengal stains seen in various ocular surface disorders.

CFC replacements: safety testing, approval for use in metered dose inhalers.

HFA-134a and HFA-227 (chlorine free hydrofluoro-alkanes) are at present in extensive nonclinical safety testing sponsored by two joint research consortia (IPACT-I, IPACT-II) of companies interested in metered dose inhalers (MDI). The rationale for toxicity testing of these CFC replacements is to predict safety of their use as drug propellants in MDI. Frequency of use, intervals and systemic exposure levels are key parameters. Intact animals and in-vitro systems repeatedly exposed to multiples of patient doses, under conditions comparable to human administration should not show adverse reactions. With an emphasis different from non-U.S. Health Authorities, the U.S. FDA insists on proof of toxic effects which may require excessive doses. This principle is questioned for essentially inert gases such as CFCs and HFA-134a and HFA-227 which only through the effects of oxygen deprivation at unreasonably high concentrations of the inhaled propellant/air mixture indirectly cause mild toxic effects in animals. Provided that no intrinsic toxic effects will be detected, chances are good that these CFC replacements will eventually be approved. In view of the estimated 5-year testing time frame and the risks involved, CFCs should remain available for MDI for some time in the future.

Mechanism of hepatotoxicity of teturam and cyanamide

The basic principle of aversive therapy in alcoholism is the use of drugs (teturam, cyanamide) that suppresses the aldehyde dehydrogenase activity in the patient's body. The excess acetaldehyde that accumulates when alcohol is taken is toxic for the organism and thereby serves as the main element in the anti-alcoholic action of the indicated drugs. The use of teturam and cyanamide for prophylactic and therapeutic purposes, however, is associated with a number of side effects, even without subsequent contact with alcohol, and this substantially reduces the effectiveness of their use. As a rule, the theories of the mechanisms of the toxic action of teturam and cyanamide are based on their reactivity and the properties of the metabolites formed in the body. Actually, both drugs and their individual metabolites are strong thiol poisons, which inhibit the activity of a number of enzymes not associated with the metabolism of ethanol itself and of acetaldehyde [3, 5, 9]. Special attention is merited by the hepatotoxicity of the indicated anti-alcoholic agents, since the state of the liver plays the main role in the biotransformation of drugs [4] and this organ itself also suffers in alcoholism [5]. According to the available literature data [3, 8, 14], against a background of the use of antabuse (teturam) and cyanamide, there is frequently latent damage to the liver, difficult to diagnose; more rarely the situation progresses to the development of severe toxic hepatitis. One of the ways to study the mechanisms of the intrinsic toxic effect of any compounds (in particular, anti-alcoholic agents) is to investigate their influence on the liver function of the healthy organism, including the determination of the pool of free amino acids in the blood plasma, recommended in recent years, since they react sensitively to slight disturbances of the functions of the organ [10-12, 16].

Effect of chlorpromazine on the function of the perfused isolated liver

The acute effect of chlorpromazine on the function of the perfused rat liver was evaluated by monitoring the removal of sulfobromophthalein (BSP) from the perfusate, the biliary excretion of the dye and the rate of bile and perfusate flow. The higher drug concentrations used, 2.5 × 10 −4, 5 × 10 −4 and 10 −3 M l . of perfusate, led to a decreased rate of removal of BSP from the perfusate and of biliary excretion of the dye, accompanied by a significant reduction of perfusate flow and bile production. These changes were porportional to the concentration of the drug. The lowest dose used, 10 −4 M l ., resulted in similar but more transient effects. In accord with other related studies, it is suggested that chlorpromazine may have an intrinsic toxic effect on the liver.